Mercury V6 Two-Stroke Engine Guide | 2.0L 2.4L 2.5L 3.0L XR2 XR4 XR6 Pro Max Mercury produced one of the longest-running and most varied families of V6 two-stroke outboards in the marine industry. From the original Black Max engines through the XR, XRi, Pro Max, Bridgeport, Optimax and Mercury Racing platforms, the basic V6 architecture evolved through several different displacements, induction systems and racing configurations. Understanding these differences is important when selecting carburetor jets, reeds, pistons, rings, cylinder-head gaskets, ignition components, fuel-system parts, and lower-unit components. A horsepower decal alone is often not enough to identify a Mercury V6 correctly. Mercury reused ratings such as 150, 175, 200, 225 and 250 HP across several different engine families. For example, the performance-oriented XR2, XR4 and XR6 progression follows three different displacement families: XR2 is associated with the 2.0L platform, XR4 with the 2.4L platform and XR6 with the 2.5L platform. Likewise, XRi identifies an electronic fuel-injected engine rather than a specific displacement, so XRi models appear in more than one V6 family. The following Buckshot Racing #77 reference chart provides a practical overview of many of the most notable Mercury V6 two-stroke engines. Model-year ranges are approximate because production periods and configurations can overlap. Mercury V6 Two-Stroke Outboard Model Chart Displacement Mercury V6 Model Approx. Model Years Description 2.0L Mercury 135 HP V6 Mid-1980s–1990s Production 2.0L V6 used in recreational, commercial, and performance applications. 2.0L Mercury 150 HP V6 Late 1970s–1990s Long-running 2.0L production V6. Later Mercury 150 models also used the larger 2.5L platform. 2.0L Mercury 150 XR2 Approx. 1985–1987 Performance-oriented carbureted 150 HP based on the 2.0L V6 platform. 2.0L Mercury 1750 Black Max Approx. 1976–1979 Early 175 HP Mercury V6 and one of the engines that established the Black Max family. 2.0L Mercury SST-120 1980s–2000s Competition 2.0L V6 used extensively in SST-120 tunnel-boat racing. 2.4L Mercury 175 HP V6 Late 1970s–early 1990s Later 175 HP production V6 using Mercury's larger 2.4L architecture. 2.4L Mercury 200 HP V6 Approx. 1978–1990 Major Mercury V6 platform offered in carbureted and EFI configurations. 2.4L Mercury 220 Laser XRi Late 1980s–early 1990s Electronic-fuel-injected 2.4L Laser/XRi performance V6. 2.4L Mercury 150 XR4 Approx. 1988–1991 Carbureted 150 HP performance engine based on the 2.4L V6. 2.4L Mercury 225 HP V6 1980s Higher-output 2.4L V6 used in selected performance configurations. 2.4L Mercury Bridgeport EFI Late 1980s–early 1990s High-performance EFI V6 known for its Bridgeport cylinder-port design and high-RPM capability. 2.4L Mercury Mod-VP 1980s Competition V6 associated with Mod-VP tunnel and performance-boat racing. 2.4L Mercury Champ 1980s–early 1990s Factory racing V6 developed for professional tunnel-boat competition. 2.4L Mercury SST-140 1980s–1990s Competition-oriented 2.4L V6 used in SST-140 racing. 2.5L Mercury 150 HP V6 Early 1990s–2000s Later-generation 150 HP production V6 based on the 2.5L platform. 2.5L Mercury 150 XR6 Approx. 1992–2005 Carbureted 150 HP performance V6 and successor to the XR4. 2.5L Mercury 150 XRi EFI 1990s Electronic-fuel-injected 150 HP version of the 2.5L V6. 2.5L Mercury 175 HP V6 Early 1990s–2000s Production 175 HP V6 using the 2.5L block family. 2.5L Mercury 175 XRi EFI 1990s EFI performance-production version of the 175 HP 2.5L V6. 2.5L Mercury 200 HP V6 Approx. 1991–mid-2000s Extremely common 2.5L platform offered in carbureted and EFI configurations. 2.5L Mercury 200 XRi EFI Early–mid 1990s Fuel-injected performance version of Mercury's 2.5L 200 HP family. 2.5L Mercury 225 Pro Max Mid-1990s–early 2000s High-performance EFI V6 combining the 2.5L platform with Mercury Racing hardware and calibration. 2.5L Mercury 225X Pro Max Early 2000s Later evolution of the 225 Pro Max high-performance EFI family. 2.5L Mercury 245 Carb Early–mid 1990s Carbureted high-performance Mercury Racing version of the 2.5L platform. 2.5L Mercury 260 EFI Early 1990s–early 2000s Iconic EFI performance engine used in lake racing, drag racing, and lightweight performance boats. 2.5L Mercury 280 ROS Late 1990s–mid-2000s High-RPM Mercury Racing EFI engine developed for Race Offshore and performance use. 2.5L Mercury 300 Drag Late 1990s–mid-2000s Competition-focused 2.5L engine developed for acceleration and drag racing. 2.5L Mercury S3000 Mid-1990s–2000s Pure racing V6 used in Formula and professional tunnel-boat competition. 2.5L Mercury Racing 200XS DFI 2000s–2010s Direct-injected Mercury Racing version of the 2.5L V6. 2.5L Mercury Racing SST-200 / 200XS SST 2000s–2010s Direct-injected 2.5L competition engine developed for SST-200 tunnel-boat racing. 3.0L Mercury 200 EFI / Optimax Mid-1990s–2010s Large-displacement V6 offered in conventional EFI and later direct-injected configurations. 3.0L Mercury 225 EFI / Optimax Mid-1990s–2010s Torque-oriented 3.0L V6 produced in EFI and Optimax configurations. 3.0L Mercury 250 EFI Mid-1990s–2000s High-output 3.0L EFI V6 used in offshore and performance applications. 3.0L Mercury 250 Pro Max Late 1990s–early 2000s Performance-oriented 3.0L EFI V6, separate from the 2.5L Pro Max family. 3.0L Mercury 300 Pro Max Late 1990s–2000 High-output 3.0L EFI performance engine preceding the 300X. 3.0L Mercury 300X Approx. 2001–2005 Mercury Racing 3.0L EFI V6 known for strong torque and high-performance use. 3.0L Mercury 250 XS 2000s Mercury Racing direct-injected 3.0L performance V6. 3.0L Mercury 250 Pro XS Mid-2000s–2010s Optimax direct-injected performance V6 designed for strong torque and high-speed applications. 3.2L Mercury Racing 300XS Mid-2000s–late 2010s Optimax-based 3.2L stroker V6 developed for increased torque and high-performance boating. 3.4L Mercury 250 HP V6 Early–mid 1980s Large-displacement two-stroke V6 designed for strong torque and heavier boats. 3.4L Mercury 275 HP V6 1980s Higher-output version of Mercury's classic 3.4L V6 platform. 3.4L Mercury 300 HP V6 Early–mid 1980s Top-output version of the classic 3.4L Mercury V6 two-stroke family. XR2, XR4 and XR6 The XR-series 150 HP engines provide a useful snapshot of Mercury V6 development. The XR2 belongs to the 2.0L carbureted family, the XR4 moved to the 2.4L carbureted platform, and the XR6 continued the performance 150 concept on the 2.5L carbureted platform. These engines are particularly important when identifying Mercury carburetor components because an XR2, XR4, and XR6 may all carry a 150 HP designation while using very different engine hardware. XRi and EFI Engines XRi refers to electronic fuel injection rather than a specific displacement. Mercury used the XRi designation on several V6 configurations, including the 2.4L Laser/XRi family and later 2.5L 150, 175, and 200 HP engines. An XRi engine does not use WH, WMV or WMH carburetors. The same is true for EFI Mercury Racing engines such as the 260 EFI, 280 ROS, 300 Drag, S3000 and 300X, as well as Optimax and other DFI engines. Carbureted vs. EFI vs. DFI Applications This distinction is important when using the chart for carburetor parts. The chart documents the broader Mercury V6 two-stroke family, but not every engine listed is a carburetor application. Carbureted Mercury engines may use WH, WMV, WMH, or other carburetor families, depending on model and production period. EFI engines use electronic fuel injection, while Optimax, 200XS, SST-200, 250 XS, Pro XS and 300XS engines use direct fuel injection and do not use conventional carburetor main jets. Buckshot Racing #77 Tech Note Mercury reused horsepower ratings across several engine generations. A 150 HP Mercury can be a 2.0L or 2.5L, a 175 HP can belong to 2.0L, 2.4L or 2.5L families, and a 200 HP V6 can be a 2.4L, 2.5L or 3.0L engine depending on its year and configuration. For accurate parts selection, identify the engine by serial number, displacement, induction system, carburetor model, and actual installed hardware. This becomes even more important on older performance engines because powerheads, front halves, carburetors, cylinder heads, and other components may have been changed during previous rebuilds. For Buckshot Racing #77 carburetor tuning products, always confirm whether the engine actually uses a compatible WH, WMV, or WMH carburetor before selecting idle-air or main-fuel jets.

The Best Way to Decode Mercury Outboard Model Codes If you own a Mercury outboard motor, understanding its model code is essential for maintenance, part replacement, and performance optimization. These codes reveal important specifications such as shaft length, starting mechanism, steering type, and additional features. This article explains the best way to decode Mercury outboard model codes. Where to Find Mercury Model Codes Locating the model code on your Mercury outboard is the first step in decoding its features. These codes are typically found in two places: Transom Bracket: The code is printed on the identification plate located on the engine’s mounting bracket, which connects the motor to the boat’s transom. Engine Block: Some models include the code on a freeze plug or stamped directly onto the engine block. This is often a small, metal disc or label near the engine’s top or side, usually the serial number. If you cannot locate the model code, see if you have your owner’s manual or the original paperwork. Understanding Mercury Model Codes Mercury outboard model codes consist of letters and numbers that represent key engine characteristics. Each letter or combination indicates specific features, including shaft length, steering type, and rotation. Accurately decoding these codes helps in choosing compatible parts, ensuring optimal performance, and enhancing engine reliability. Key Letter Definitions in Mercury Model Codes To decode a Mercury outboard model code, understanding the meaning of its letters is crucial. Here’s what each letter represents: C: Counter-rotating (left-hand propeller rotation) for twin-engine setups. E: Electric start H: Handle, tiller steering L: Long shaft (20 inches) LL: Long-long shaft (22.5 inches) M: Manual start O: Oil injection standard PT: Power trim standard RC: Remote control steering S: Short-long shaft (17.5 inches) XL: Extra-long shaft (25 inches) XXL: Extra-extra-long shaft (30 inches) Shaft Lengths in Mercury Outboards Choosing the right shaft length is one of the best ways to optimize your boat’s performance. Mercury outboards are available in various shaft lengths to match different transom heights: Short Shaft (S): 15 inches Long Shaft (L): 20 inches Long-Long Shaft (LL): 22.5 inches Short-Long Shaft (MSL): 17.5 inches Extra-Long Shaft (XL): 25 inches Extra-Extra-Long Shaft (XXL): 30 inches Matching the shaft length to your boat’s transom height ensures the cavitation plate is properly aligned with the hull bottom, improving stability and propulsion. Detailed Mercury Model Code Configurations Here are examples of model codes and their specific configurations: CXL: Extra-long shaft (25 inches), counter-rotating (left-hand) propeller. Ideal for V-6 twin-engine setups. CXXL: Extra-extra-long shaft (30 inches), counter-rotating (left-hand) propeller, perfect for larger boats with twin-engine configurations. E: Electric start, short shaft (15 inches), remote control steering for small to medium boats. EH: Electric start, short shaft (15 inches), tiller handle steering for direct manual operation. EHO: Electric start, short shaft (15 inches), tiller handle steering, and oil injection for enhanced performance. EL: Electric start, long shaft (20 inches), remote control steering for medium to larger vessels. ELH: Electric start, long shaft (20 inches), tiller handle steering for precise manual control. ELHO: Electric start, long shaft (20 inches), tiller handle steering, oil injection for superior engine lubrication. ELHPT: Electric start, long shaft (20 inches), tiller handle steering, power trim for easier angle adjustments. ELHPTO: Electric start, long shaft (20 inches), tiller handle steering, power trim, and oil injection for maximum control. EXLH: Electric start, extra-long shaft (25 inches), tiller handle steering, suitable for larger engines. EXLHPT: Electric start, extra-long shaft (25 inches), tiller handle steering, power trim for premium handling. EXLHPTO: Electric start, extra-long shaft (25 inches), tiller handle steering, power trim, and oil injection for ultimate performance. MRC: Manual start, short shaft (15 inches), remote control steering for small boats. ML: Manual start, long shaft (20 inches), tiller handle steering for medium-sized boats. XL: Extra-long shaft (25 inches), right-hand propeller rotation for V-6 models. XXL: Extra-extra-long shaft (30 inches), right-hand propeller rotation for large V-6 models. The Best Way to Use Mercury Model Codes Find the Model Code: Look for the model code on the transom bracket or a freeze plug on the engine block. Identify the Shaft Length: Measure your boat's transom height and match it to the correct shaft length (15", 20", 25", or 30"). Decode Features: Use the letter definitions to understand key features like steering type, start mechanism, or prop rotation. Match Components: Ensure that parts such as propellers and controls are compatible parts with your outboard's configuration. Why Decoding Matters Decoding your Mercury outboard model code ensures that you select the right engine for your boat and its operating conditions. This is the best way to optimize performance, simplify maintenance, and prolong the engine’s life. Use this guide to decode your Mercury model code to keep your outboard running strong.

A History of Technical Advancements The Mercury V6 2-stroke outboard engine series has been at the forefront of marine technology since its inception in 1976. Known for high performance and reliability, these engines have undergone significant advancements, making them a staple for boaters and racers alike. This article delves into the evolution of the Mercury V6, highlighting key models and technological innovations that have shaped its legacy. 1976 - The Birth of the V6 Outboard Mercury Marine launched the 1750 2.0 Liter 175 HP 2-Stroke V6 Outboard in 1976, superseding the inline 6 “Tower of Power” at the top of the food chain, marking a pivotal shift in outboard design. With a 2.0-liter displacement, this engine combined compactness and power, setting a benchmark for future models. Its carbureted system provided an excellent power-to-weight ratio, making it a popular choice for recreational boating. Late 1970s - Expanding Power Options In the late 1970s, Mercury expanded its V6 lineup with the 150 HP and 200 HP models. The 150 engines maintained the 2.0-liter displacement while the 200 and 225 HP increased displacement to 2.4 Liters and featured enhanced tuning and carburetor setups, catering to various performance needs. These engines laid the groundwork for a more diverse product range in high-performance boating. 1980s - High-Performance Innovation and The Black Max Series Launched in the early 1980s, the Black Max series offered an aesthetic appeal with high-performance features. Available in 150 HP, 175 HP, and 200 HP variants, the Black Max and later Mod VP Race engines were known for their distinctive black paint and advanced compression ratios, providing faster acceleration and improved speed. The 1980s also saw the introduction and beginning of the XR series, including the XR2, and XR4, and later in the 1990s the XR6 model, designed specifically for high-performance applications. The XR series introduced several advancements: XR2 (150 HP 2.0 Liter): Enhanced mid-range power and acceleration. XR4 (150 HP 2.4 Liter): A lighter gearcase contributed to faster speeds. XR6 (150 HP 2.5 Liter): Optimized for top-end performance with refined tuning. The introduction of the 2.0 Liter Champ and 2.4 Liter Bridgeport engines further showcased Mercury's racing capabilities, featuring high RPM capabilities and unique porting to maximize airflow. These engine further solidified Mercury's reputation in competitive racing. 1980s to 1990s - The Shift to EFI Technology Mercury began integrating Electronic Fuel Injection (EFI) in the late 1980s, revolutionizing fuel delivery in its engines. The 2.4L EFI and later 2.5L EFI models featured smoother operation, better throttle response, and enhanced fuel economy, appealing to both recreational boaters and performance enthusiasts. 1990s - The Pro Max Series and Optimax Direct Injection The introduction of the 2.5L V6 engine, along with the Pro Max 150, 200, and 225 models, marked a new era of performance. These engines featured high compression, lightweight components, and specific tuning for maximum RPMs. In the mid-1990s, the Optimax line was introduced, utilizing Direct Fuel Injection (DFI) to improve fuel efficiency and reduce emissions while maintaining the performance characteristics of 2-stroke engines. Models like the Optimax 135, 150, 175, 200, 225, and 250 became widely popular among eco-conscious consumers. 2000s - The Racing XS Models The introduction of the 3.0 Liter 250 XS and 3.2 Liter 300 XS models represented the pinnacle of Mercury's 2-stroke racing technology. Designed for competitive racing, these engines featured lightweight designs and advanced electronics, ensuring precise engine control and maximum performance. Legacy and Performance Parts Availability The Mercury V6 2-stroke outboard engines, including the iconic Black Max series, have made a lasting impact on the boating industry. Known for their exceptional reliability and performance, these engines continue to be a favorite among enthusiasts and racers. For those looking to enhance their outboard’s performance, a wide range of performance parts are available here at Buckshot Racing #77, including high-performance pistons, propellers, fuel systems, gaskets, CDI ignition components, and performance billet components. Whether you’re upgrading a Mercury V6 or maintaining a classic Black Max, the right parts can significantly enhance speed and handling. From the original 1750 / 175 HP model to the advanced racing variants, the Mercury V6 2-stroke outboards represent a remarkable journey of innovation and engineering excellence. Their continued popularity in the boating community reflects not only their performance capabilities but also the quality of parts available for upgrades and maintenance. Explore our selection of high-performance parts to keep your Mercury V6 running at its best! Here is a more (but not fully) complete list of notable V6 Merc 2-stroke motors: 2.0-Liter Displacement Models Mercury 150 HP V6 Mercury 175 HP V6 Mercury SST-120 (2.0L) 2.4-Liter Displacement Models Mercury 200 HP V6 5-petal Mercury 225 HP V6 7-petal Mercury 240 HP V6 Bridgeport Mercury Mod VP (2.4L) Mercury Champ (2.4L) Mercury SST-140 (2.4L) 2.5-Liter Displacement Models Mercury 200 HP V6 (2.5L) Mercury 225 HP Pro Max V6 (2.5L) Mercury 260 HP EFI V6 (2.5L) Mercury 280 HP ROS V6 (2.5L) Mercury 300 HP Drag V6 (2.5L) Mercury Pro Max 225 HP V6 Mercury Pro Max 250 HP V6 3.0-Liter Displacement Models Mercury 3.4 Liter Mercury 300 Pro Max V6 (3.0L) Mercury 300X VP (3.0L) Mercury 250 Pro XS V6 (3.0L) Mercury 300 XS Stroker V6 (3.2L)

The history of Mercury 2-stroke outboard carburetors, specifically the transition between the WH, WMH, and WMV series, reflects the evolution of carburetion technology aimed at enhancing engine performance, efficiency, and reliability. 1. WH Series Carburetors: Introduction and Features: The WH series, introduced in the late 1970s and early 1980s, was known for its "Wide Horn" design, which allowed for greater air intake and improved fuel-air mixing. These carburetors were commonly used in high-performance and racing engines, particularly in Mercury's V6 models. The WH carburetors featured multiple venturis and larger throttle bores, enabling more precise fuel metering and higher power output. Applications: They were widely used in high-performance outboards such as the SST-140, SST-120, F1 / F200 tunnel boat and Pro Carb drag race classes, favored by enthusiasts and racers for their ability to provide a rich fuel mixture necessary for maximizing power. 2. WMH Series Carburetors: Development and Design Changes: The WMH series succeeded the WH series and was introduced in the late 1980s and early 1990s. This series featured a more compact design and refined 3-stage fuel metering systems. The WMH carburetors aimed to improve fuel efficiency and reduce emissions while maintaining performance. Technological Advancements: The WMH carburetors incorporated advances in carburetor technology, such as improved float and needle designs, which enhanced fuel flow control. They also featured better atomization of fuel, contributing to more efficient combustion. Usage: While orignal found on the the 2.5 Liter 150, 175, 200 and 245 HP outboards, they are still used in performance and drag race applications, the WMH series was also found in a broader range of outboard engines, including those designed for recreational use. 3. WMV Series Carburetors: Introduction and Characteristics: The WMV series represented further refinement in carburetor technology. Introduced in the mid-1990s, these carburetors focused on meeting stricter environmental regulations by reducing emissions and improving fuel economy. The WMV carburetors featured even more precise fuel metering and better control over air-fuel mixtures across different engine speeds and loads. Emission Standards and Efficiency: The development of the WMV series was driven by the need to comply with increasingly stringent emission standards. These carburetors were designed to optimize the air-fuel mixture for cleaner combustion, thus reducing pollutants like hydrocarbons and carbon monoxide. Wider Application: The WMV series was used across a range of Mercury 2-stroke outboards, including the SST-120, from small engines to larger 3.0 Liters, high-output models, reflecting a shift towards more environmentally friendly and fuel-efficient designs. Transition to Modern Fuel Systems: The introduction of electronic fuel injection (EFI) and direct fuel injection (DFI) systems marked the end of the carburetor era for Mercury's 2-stroke outboards. These systems offered superior fuel management, better performance, and significantly reduced emissions. EFI and DFI systems could precisely control the amount of fuel injected into the combustion chamber, leading to more efficient combustion and cleaner engine operation. Legacy: The WH, WMH, and WMV series carburetors represent significant milestones in the evolution of Mercury's 2-stroke outboard engines. Each series reflected the technological advancements and regulatory changes of its time, pushing the boundaries of performance and efficiency. Today, while these carburetors are largely replaced by more modern fuel injection systems, they are still valued by collectors and performance enthusiasts for not only their role in the history of marine engines but also the price point of building fast and reliable powerhead. Resources:

Photo reproduced from Powerboat, accompanying Steve Silver’s “The Record Falls Again.” Photographer unidentified in the supplied pages. Buckshot Racing #77 | Outboard Racing History On October 5, 1983, Bob Cox and Dean Pink completed the Mississippi River run from New Orleans to St. Louis in 23 hours, 9 minutes. Their boat was a 19-foot Charger Foxfire bass boat, powered by a single cross-flow 235-hp Johnson outboard. It was an extraordinary result for a rig that looked more at home heading to a fishing spot than challenging a long-distance speed record. The achievement displaced Michael Reagan’s earlier mark. Steve Silver’s Powerboat article, “The Record Falls Again,” reported Reagan’s time as 25 hours, 7 minutes. On that basis, Cox and Pink cut 1 hour, 58 minutes from the journey—almost two hours. A Small Boat With a Big Job Reagan’s attempt had used a 38-foot Wellcraft Scarab and a substantial support operation. Cox and Pink chose a far smaller, open-cockpit boat and a leaner approach. The magazine described their effort as having no backup boats and no large team of mechanics. Once they were underway, a major mechanical problem could end the attempt. Cox was president of Charger Boats, and the Foxfire gave him a chance to demonstrate what a bass boat could accomplish outside its usual role. Silver described a lightweight hull that came onto plane quickly. For a trip requiring repeated stops, that characteristic was useful: the boat had to get moving again efficiently, then keep covering miles. Experience Before the Record Cox and Pink had already made the trip in 1978. Powerboat reported a daylight running time of 20 hours, 25 minutes, with an overnight stop in Greenville, Mississippi. That earlier result gave them experience on the route, but it belongs in a different category from the 1983 elapsed-time achievement. A running-time total that excludes an overnight stop cannot be compared directly with a journey’s total elapsed time. The 1983 challenge demanded more than a fast hull. They needed an engine that would keep performing, a boat they could manage over a long distance, and stops that would not consume their margin. The magazine emphasized the consequences of a breakdown: repairs would have to be handled quickly on the water, while a serious failure would finish the run. The Record in Numbers Metric Michael Reagan Bob Cox and Dean Pink Run year 1982 1983 Boat 38-foot Wellcraft Scarab 19-foot Charger Foxfire Reported elapsed time 25 hours, 7 minutes* 23 hours, 9 minutes Distance used for comparison 1,027 miles 1,027 miles Calculated overall average 40.9 mph 44.4 mph Cox and Pink’s improvement: 1 hour, 58 minutes—approximately 7.8% less elapsed time using Powerboat’s reported baseline. The 44.4-mph figure is a calculated overall average: 1,027 miles divided by 23 hours, 9 minutes. It includes the full elapsed time of the journey, including stops. It does not represent the boat’s top speed or its average speed while underway. Historical timing note: Powerboat gives Reagan’s time as 25:07. Dean Klinkenberg’s later history lists 25:11, which would produce a 2-hour, 2-minute improvement. This article and its chart use 25:07 to preserve the comparison printed in the supplied magazine pages. Why Buckshot Racing #77 Is Revisiting This Story For outboard enthusiasts, this is a compelling example of a small boat taking on a large task. The lesson we draw from it is that usable performance combines hull behavior, dependable power, preparation, and the ability to keep moving. Every minute stopped counts against the same clock as every mile underway. Buckshot Racing #77 celebrates the people and machines that helped shape outboard performance. Cox and Pink’s Mississippi run deserves a place in that history: two drivers, one bass boat and one outboard completing more than a thousand miles in less than a day. Buckshot Racing #77, Bob Cox, Dean Pink, Mississippi River record, Charger Foxfire, Charger Boats, Johnson 235, Johnson outboards, bass boat history, outboard racing history, endurance boat racing, New Orleans to St. Louis, Michael Reagan, vintage powerboats Source Credit and Editorial Note This original Buckshot Racing #77 historical retelling is based on two supplied pages of Steve Silver’s “The Record Falls Again” in Powerboat, with historical cross-checking against Dean Klinkenberg’s “Chasing the Robert E. Lee: Boat Races on the Mississippi River,” published in The Confluence, 2020, Volume 11, Issue 2, Article 2. The complete Powerboat article and its continuation on page 63 were not located, and the magazine issue date remains unconfirmed. No missing passages, quotations, engine modifications, fuel totals, or stop schedules have been reconstructed. The accompanying artwork consists of modern historical illustrations rather than archival photographs. Buckshot Racing #77 branding identifies this editorial presentation.

How to Find Your Outboard Gear Ratio | Mercury and Mercury Racing If you run a Mercury or Mercury Racing outboard, this guide shows you how to find the gear ratio of the lower unit you actually have. You will learn the spin test, the tooth count, the ratios Mercury and Mercury Racing cases commonly use, and how to use the Buckshot Racing #77 gear ratio calculator. The short answer: Turn the flywheel, count the prop, and divide. That is the gear ratio. On a Mercury V6 it is usually 1.87 or 2.00, unless the case is an OptiMax 1.78, a 3.0 liter Sport Master 1.62, or a Mercury Racing four-stroke. Guess it and the slip number is not right. Gear ratio is how many times the crank turns for one turn of the propeller. A 1.87:1 lower turns the crank 1.87 times every time the prop goes around. That one number sets prop RPM, the pitch the motor can pull, and whether a slip calculator is telling you the truth. Lowers get swapped. A 1.87 and a 2.00 will wear the same cowling on a Mercury 2.0, 2.4, or 2.5 liter. A Mercury Racing 300X that left as a Sport Master can come back as a Torque Master. Read the case in your hands, not the badge on the cowl. Why a wrong gear ratio wrecks the prop call Prop speed is engine speed divided by the ratio. Theoretical speed uses that prop speed and the pitch on the hub. Prop RPM = engine RPM ÷ gear ratio Theoretical mph = (prop RPM × pitch in inches) ÷ 1056 At 5600 RPM a 1.87 case is turning the prop about 2,995 RPM. A 1.62 Sport Master is turning it about 3,457 RPM. Same tach, same 26-inch prop, two different boats. Put 1.87 into the slip calculator on that Sport Master and you will chase a pitch problem you do not have. A lower number spins the prop faster, so it needs less pitch for the same speed. A 2.00:1 spins it slower, multiplies torque, and can swing a taller prop. That is why a ratio swap changes hole shot even when the hub stamp never moved. The spin test: find the ratio on the boat Do this dead. Cowl off. Plug leads off and plugs out, so a two-stroke cannot fire and turns easily. Battery disconnected. Lanyard off. Stay off the prop. Hand turn only, never the starter. Mark one blade and a fixed spot on the anti-ventilation plate or skeg. Mark the flywheel the same way. Shift into forward. Neutral unhooks the prop shaft, and you will count a freewheel. Put a socket on the flywheel nut and turn in the normal direction, clockwise looking down on most Mercury flywheels. Take the slack out, then start the count. Turn a round number of flywheel revolutions. Three is a first pass. Five or six is the number you trust. Read the prop mark. Half a turn is 0.50. Twelve o'clock to four o'clock is about 0.33. Divide flywheel turns by prop turns. Three flywheel turns and 1.60 prop turns is 1.88:1. That is a 1.87 with a sloppy partial turn, not a secret gearset. Spin it again and round to the published ratio it is sitting on. How to use the Buckshot gear ratio calculator Pick the tab that matches what you have in front of you. Results update as you type, so there is no calculate button. Spin test tab. Use this on the boat or trailer. Enter the flywheel turns you counted and how far the propeller turned, in decimals. The page loads example values (3 turns and 1.60 prop turns), so replace both with your own counts. Optional engine RPM. Enter your wide-open-throttle tach reading to see prop RPM at that speed. Read the result. You get the ratio and a note naming the common Mercury and Mercury Racing ratios it sits closest to. A result of 1.86 or 1.88 is a partial-turn miss on a 1.87, so repeat with five or six flywheel turns before you round to a published ratio. Tooth count tab. Use this with the case open. Enter driven (forward) gear teeth and pinion teeth. Count only the gear set that sets the reduction. Prop RPM check tab. The ratio from either method carries over automatically. Enter your engine RPM and pitch to see prop shaft RPM and theoretical speed at 0 percent slip. Take it to the slip calculator. Run the confirmed ratio, pitch, RPM, and GPS speed through the Buckshot prop slip calculator. The calculator only does the division. The count has to come off the boat, and the ratio should be confirmed against the serial number and the parts listing. Tooth count, and when the parts book is enough With the case open, divide forward-gear teeth by pinion teeth. A 28-tooth forward gear on a 15-tooth pinion is 1.87:1. That is the cleanest number you will get, as long as you are counting the gear set that actually sets the ratio. Some drives stack an upper reduction on a lower set, so one pair is not always the whole story. The parts listing is the third check. Match the gearcase and serial number, then treat the listed ratio as a candidate. Sport Master, Torque Master, Fleet Master, 5.44 HD, and R-Drive are not the same number, and a swapped lower will not match the cowling. Mercury 2.0, 2.4, and 2.5 liter two-strokes This is the family we see every week: Mercury 2.0, 2.4, and 2.5 liter V6 engines, including Pro Max 225, 260 EFI, and 280 ROS. Most cases are 1.87:1 or 2.00:1. The 2.5 liter OptiMax is the odd one, at 1.78:1. It is a 2.5, but it is not a 1.87. If slip looks impossible on an OptiMax 2.5, check for 1.78 before you condemn the prop. Mercury 3.0 liter two-strokes The 300 family steps down. Sport Master cases on the 300, 300 Pro Max, 300X, 300 XS, and 250 XS are commonly 1.62:1. Torque Master and Fleet Master cases are commonly 1.75:1. A 300X with a swapped Torque Master is a 1.75 boat until the spin test says otherwise. Mercury Racing 200R, 250R, 300R, 450R, and 500R Ratio follows the gearcase, not the horsepower badge. The Mercury Racing 450R and 500R are simple at 1.60:1. The 300R is not: a Torque Master at 1.75 and a Sport Master at 1.60 will not want the same pitch. If you cannot read the case, spin it. Engine Gearcase Ratio Mercury 2.0 / 2.4 / 2.5, Pro Max 225, 260 EFI, 280 ROS Most cases 1.87:1 or 2.00:1 Mercury 2.5 OptiMax OptiMax case 1.78:1 Mercury 300, 300 Pro Max, 300X, 300 XS, 250 XS Sport Master 1.62:1 Mercury 3.0 liter two-stroke Torque Master or Fleet Master 1.75:1 Mercury Racing 200R Torque Master or Sport Master 1.75:1 Mercury Racing 250R Sport Master (CMS spec) 1.75:1 Mercury Racing 300R Torque Master 1.75:1 Mercury Racing 300R Sport Master 1.60:1 or 1.75:1 Mercury Racing 300R Advanced MidSection 1.85:1 or 1.60:1 Mercury Racing 450R Sport Master or 5.44 HD 1.60:1 Mercury Racing 500R R-Drive or R-Drive Sport 1.60:1 What each ratio does at 5600 RPM Ratio Prop RPM What it means on the water 1.60:1 3,500 Mercury Racing 450R, 500R, some 300R Sport Master cases. Fast prop, less pitch for the same speed. 1.62:1 3,457 Mercury 3.0 liter Sport Master. 1.75:1 3,200 Mercury 3.0 liter Torque Master, Mercury Racing 200R, 300R Torque Master. 1.78:1 3,146 Mercury 2.5 OptiMax. Do not call this a 1.87. 1.87:1 2,995 The usual Mercury 2.0, 2.4, and 2.5 liter case. 2.00:1 2,800 Slower prop, more torque, takes more pitch. Worked example: how a wrong ratio shows up in slip Slip % = (theoretical mph − GPS mph) ÷ theoretical mph × 100 A Mercury 3.0 liter Sport Master boat turns 5,800 RPM at wide open throttle on a 27-inch pitch prop. The GPS reads 80 mph. The owner assumes the usual 1.87 case. Using the wrong ratio (1.87): Prop RPM = 5,800 ÷ 1.87 = 3,102 Theoretical mph = 3,102 × 27 ÷ 1056 = 79.3 Slip = (79.3 − 80) ÷ 79.3 = −0.9 percent Negative slip is not possible on a real hull. The boat is not outrunning its prop. The ratio is wrong. Using the real ratio (1.62, confirmed by spin test): Prop RPM = 5,800 ÷ 1.62 = 3,580 Theoretical mph = 3,580 × 27 ÷ 1056 = 91.5 Slip = (91.5 − 80) ÷ 91.5 = 12.6 percent That is a believable number, and now the pitch call is based on something real. Same boat, same tach, same GPS. The only thing that changed was the ratio. Then run the slip Once the ratio is honest, put pitch, RPM, and GPS through the Buckshot prop slip calculator. Negative slip, or 30 percent on a clean race hull, usually means the ratio or the tach is wrong. The GPS is rarely the liar. FAQ gear ratio questions we get in the shop How do I find my outboard gear ratio without pulling the case? Use the spin test. Forward gear, engine dead, flywheel turns divided by prop turns. Count five or six flywheel turns if the prop stops between marks. Can I read the ratio off the horsepower badge? No. Ratio follows the gearcase. Cases get swapped, and two Mercury 300s in the same pits can be 1.62 and 1.75. What if the spin test says 1.86 or 1.88? That is a partial-turn miss on a 1.87. Count more flywheel turns and round to the published ratio. Which Mercury Racing 300R ratio do I enter? Torque Master is 1.75:1. Sport Master is 1.60:1 or 1.75:1. Advanced MidSection is 1.85:1 or 1.60:1. If the case is not marked, spin it. What gear ratio does a Mercury OptiMax 2.5 have? It is commonly 1.78:1, not the 1.87 you see on most Mercury 2.0, 2.4, and 2.5 liter V6 cases. Confirm with the serial number and a spin test.

Learn how to use the Buckshot Racing #77 Prop Slip Calculator and Theoretical Setup tab for Mercury outboards, F1 tunnel boats, bass boats, offshore boats, drag boats, cats, lake boats and high-performance marine setups. Prop slip is one of the fastest ways to turn a GPS speed number into a useful boat setup decision. Whether you run a Mercury Racing outboard, F1 tunnel boat, bass boat, offshore vee-bottom, center console, cat, drag boat, lake boat, river boat, or high-performance fishing boat, the Buckshot Racing #77 Prop Slip Calculator helps you understand how your propeller pitch, gear ratio, engine RPM, GPS speed, engine height, trim, and boat load are working together. Prop slip is not a trophy number. It is a setup tool. A lower number is not always better, and a higher number is not always wrong. The right slip number depends on the boat, propeller style, gearcase height, load, water conditions, and how the hull carries itself at speed. Start Here: Which Calculator Tab Should You Use? Use the Propeller Slip tab when you already have a real test pass. This tab tells you what your current setup is doing. Enter your prop pitch, gear ratio, engine RPM and GPS speed. The calculator will show your prop RPM, theoretical speed and prop slip percentage. Use the Theoretical Setup tab when you want to compare possible changes before swapping parts. This tab is for “what-if” setup work. Use it to compare a different prop pitch, RPM target, gear ratio, or expected speed based on a known slip number. The Best Prop Slip Calculator Tool (Free Below) Step 1: Make a Clean GPS Pass Before using the calculator, make one clean wide-open-throttle pass with the boat fully warmed up and running normally. Record the GPS speed and RPM from the same pass. Do not use RPM from one run and GPS speed from another run. For the best data, test in calm water, avoid heavy current, and make one pass in each direction. If possible, average the GPS speed from both directions. Record fuel load, passenger load, trim setting, jack plate height, propeller pitch, and gear ratio. A good slip number starts with good data. If the input numbers are wrong, the calculator result will be wrong. Step 2: Use the Propeller Slip Tab Open the Propeller Slip tab and enter four numbers. Enter the propeller pitch stamped on the prop. If the prop has heavy cup, blade work, or a lab finish, remember that it may act like more pitch than the number stamped on the hub. Enter the gear ratio as a simple number, such as 1.62, 1.75, 1.87, or 2.00. Do not enter it as “1.75:1.” Gear ratio matters because the propeller turns slower than the engine crankshaft. Enter the engine RPM from a reliable tachometer. A tach that is off by a few percent can change the slip number enough to send you in the wrong direction. Enter the GPS speed from the same run. Use GPS, not a dash speedometer, pitot tube, or paddle-wheel speed reading. After you enter the numbers, the calculator will show your prop RPM, theoretical speed and slip percentage. This is your baseline. Step 3: Understand the Slip Number Prop slip is the difference between the theoretical speed the propeller should run and the actual speed the boat runs on GPS. Every propeller needs some slip to create thrust. Zero slip is not realistic, and negative slip usually means the data needs to be checked. For many high-performance outboard boats, 5% to 10% slip is a strong range. Some very efficient race boats, drag boats and light cats may run lower. Offshore boats, center consoles and heavier loaded boats may run higher. Some F1 tunnel boats, surface-running cleaver setups and high engine-height race applications may show higher calculated slip because the propeller is running high, partially surfaced, or in aerated water. That is why prop slip should always be judged by application. A bass boat, Sport Master tunnel boat, F1 hull, offshore vee-bottom, pontoon, drag boat and center console should not all be judged by the same target number. Step 4: Go to the Theoretical Setup Tab After you calculate your current slip, go to the Theoretical Setup tab. This is where the calculator becomes a setup planning tool. Use your real slip number as the target slip. For example, if your current setup calculates at 6.5% slip, enter 6.5% into the Theoretical Setup tab. Then change pitch, RPM, or gear ratio to compare possible setups. This tab helps answer real-world setup questions before you start swapping parts. It can help you estimate whether a 26-pitch prop may be faster than a 24-pitch prop after the expected RPM drop. It can help show whether a gear ratio change will require a different prop. It can help you decide what propeller to bring to the lake, race site, or test session. The Theoretical Setup tab does not guarantee the boat will run that exact speed. It assumes the new setup can hold the same slip. If the new prop ventilates, loads the engine too hard, carries the hull differently, loses water pressure, or changes handling, the actual GPS speed may be different. Use this tab as a smart planning guide, not a promise. Typical Prop Slip Ranges Use these ranges as general guides, not hard rules. Hull design, load, water conditions, propeller type, engine height, trim and setback all affect slip. Boat Type / Application Typical WOT Slip Range How to Read It Light race boat, drag boat, efficient cat 2%–6% Very hooked up; data must be accurate Bass boat or lake performance boat 5%–10% Strong all-around performance range Ski boat or family performance setup 6%–12% Good balance of acceleration and speed Offshore vee-bottom, center console, sportfish 8%–15% Load, wind and sea conditions matter Pontoon, work boat, heavy loaded hull 12%–18% Higher slip can be normal under load F1 tunnel, surface-running prop, high engine-height race setup 12%–25% Can be normal when the prop is high, surfaced, or aerated Over 20% on a normal submerged-prop setup Investigate Possible ventilation, wrong pitch, height, load, or blade issue A 20% slip number may be a problem on a normal submerged-prop bass boat. That same number may be acceptable on an F1 tunnel boat or surface-running race setup if the boat is fast, stable, carrying correctly, maintaining water pressure and turning the correct RPM. Why Some Fast Boats Show Higher Slip Some high-performance boats run the gearcase high to reduce drag. Some use cleavers, choppers, semi-surfacing propellers, or lab-finished wheels. Some hulls carry more of the boat on air or lift instead of pushing the full hull through the water. In those setups, the propeller may not be fully buried. It may be running partially surfaced or in aerated water. The calculated slip number can look higher even when the boat is running correctly. This is common in certain tunnel hull, cat, F1, drag and race applications. It can also show up on high engine-height lake boats and light performance hulls. The correct question is not “Is the slip number low?” The correct question is “Is the boat faster, safer, stable, in the RPM range and carrying correctly?” What Negative Slip Means If the calculator shows negative slip, check the data. The boat is not more than 100% efficient. Negative slip usually means the gear ratio is wrong, the tach is inaccurate, the GPS number is wrong, the pitch was entered incorrectly, or the propeller has more effective pitch than the stamp shows. Cup, rake, lab finishing and blade work can make a propeller act taller. If you are running a heavily cupped or worked propeller and the slip number looks too low or negative, try adding half an inch or one inch of effective pitch in the calculator and see if the number makes more sense. How to Use the Results If slip is high, RPM is high and speed is low, the propeller may not be holding water. The setup may need more cup, more blade area, a lower engine height, less positive trim, or a different propeller style. If slip is high and RPM is low, the engine may be overloaded. The boat may need less pitch, less load, a different propeller, or a closer look at gearcase drag and blade condition. If slip is acceptable but RPM is too high, the engine may be able to pull more pitch. Go to the Theoretical Setup tab and compare the next pitch before testing. If slip is acceptable but RPM is too low, the boat may be over-propped. Use the Theoretical Setup tab to compare less pitch and see how the speed estimate changes when RPM comes back into the powerband. If hole shot is poor but wide-open slip looks good, remember that WOT slip does not describe launch. Blade count, diameter, rake, cup, ventilation and engine height all affect the first 50 feet. What to Change First Start with pitch. More pitch usually lowers RPM and may add speed if the engine can pull it. Less pitch usually raises RPM and can improve acceleration. Cup adds bite and often increases effective pitch. A propeller with more cup may reduce slip without changing the stamped pitch number. Diameter and blade area help carry load. Heavier boats, offshore boats, loaded fishing boats and rough-water setups may need more blade area. Engine height changes how much gearcase and propeller are in the water. Raising the engine can reduce drag and improve speed, but it can also increase slip if the propeller starts to ventilate. Lowering the engine can improve bite and water pressure but may add drag. Trim changes hull attitude. A little positive trim can free up the hull. Too much trim can raise slip, blow out the propeller and make the boat unstable. Gear ratio changes prop shaft RPM. After any gearcase swap, go back to the calculator before blaming the propeller. Best Testing Method Make one baseline run and record pitch, gear ratio, RPM, GPS speed, engine height, trim, fuel load and passenger load. Use the Propeller Slip tab to calculate your current slip. Use the Theoretical Setup tab to compare the next pitch, gear ratio, or RPM target before changing parts. Make only one change at a time. Do not change pitch, trim, jack plate height and load all at once. Run the same course again, preferably in both directions, and average the GPS speed. Keep the change only if the boat gains speed, keeps safe water pressure, stays stable, and keeps the engine in the correct RPM range. Common Mistakes The most common mistake is using bad data. Do not use the dash speedometer instead of GPS. Do not guess the gear ratio. Do not mix GPS speed from one pass with RPM from another. Do not compare a light-fuel solo pass to a full-load run and expect the same slip. Another mistake is chasing the lowest slip number instead of the fastest, safest setup. A boat can show a pretty slip number and still be slower because the engine is out of its powerband or the hull is not carrying correctly. A third mistake is ignoring the Theoretical Setup tab. That tab can save time, fuel and prop swaps by showing whether a pitch or gear ratio change makes sense before you test it. Bottom Line The Buckshot Racing #77 Prop Slip Calculator is a setup tool for Mercury outboards, Mercury Racing engines, F1 tunnel boats, bass boats, offshore boats, cats, drag boats, lake boats, river boats, and high-performance marine setups. Start with the Propeller Slip tab to calculate your real-world slip from an actual GPS run. Then use the Theoretical Setup tab to compare the next propeller, gear ratio, RPM target, or setup change before testing. The goal is not the lowest slip number. The goal is the best honest setup: correct RPM, safe water pressure, stable handling, strong acceleration, and the best real GPS speed for your boat. By routinely using a prop slip calculator, racers can refine their setup for maximum speed, better fuel efficiency, and enhanced handling, ultimately leading to better results on the water.

Buckshot Racing #77 Mercury V6 cylinder head fly-cut reference chart showing approximate machining depth by pocket diameter and CC reduction for Mercury 2.0L, 2.4L and 2.5L two-stroke performance cylinder heads. One of the most common questions when machining a Mercury V6 two-stroke cylinder head is how many thousandths need to be removed to reduce the combustion chamber by one CC. There is no single number that applies to every Mercury 2.0L, 2.4L or 2.5L cylinder head because the amount of volume removed depends heavily on the diameter and shape of the combustion-chamber pocket. The basic rule is simple: the larger the effective pocket diameter, the more volume is removed with each thousandth of an inch cut from the head. A smaller pocket therefore requires a deeper cut to remove the same amount of chamber volume. For example, a head with an effective 2.250" pocket diameter requires approximately .0153" of material removal per CC. Increase the effective diameter to 2.500" and that drops to approximately .0124" per CC. At 3.000", only about .0086" is required per CC. The Buckshot Racing #77 reference below provides a practical starting point for Mercury V6 cylinder-head machining. Quick Reference — Approximate Cut Per CC Pocket Diameter Approximate Cut for 1 CC 2.000" .0194" / 19.4 thousandths 2.250" .0153" / 15.3 thousandths 2.375" (2-3/8") .0138" / 13.8 thousandths 2.500" .0124" / 12.4 thousandths 2.750" .0103" / 10.3 thousandths 3.000" .0086" / 8.6 thousandths These numbers give you an easy shop rule: a larger pocket removes more CC per thousandth, so it requires less machining to achieve the same CC reduction. Mercury V6 Fly-Cut Reference Chart The following chart expands the calculation from a 1 CC reduction through a 10 CC reduction. Find the approximate effective pocket diameter across the top, then follow that column down to the number of CCs you want to remove. CC Reduction 2.000" 2.250" 2.375" 2.500" 2.750" 3.000" 1 CC .0194" .0153" .0138" .0124" .0103" .0086" 2 CC .0389" .0307" .0275" .0249" .0205" .0172" 3 CC .0583" .0460" .0413" .0373" .0308" .0258" 4 CC .0778" .0614" .0551" .0497" .0411" .0345" 5 CC .0972" .0767" .0688" .0622" .0513" .0431" 6 CC .1167" .0921" .0826" .0746" .0616" .0517" 7 CC .1361" .1074" .0964" .0870" .0719" .0603" 8 CC .1556" .1228" .1101" .0995" .0821" .0690" 9 CC .1750" .1381" .1239" .1119" .0924" .0776" 10 CC .1945" .1535" .1377" .1243" .1027" .0862" These values are mathematical reference numbers. They are intended to help estimate an initial fly cut and should not be interpreted as the amount that can safely be removed from every Mercury cylinder head. Why Pocket Diameter Matters Mercury produced many different V6 two-stroke cylinder heads across the 2.0L, 2.4L and 2.5L engine families. Chamber diameter, depth, squish area, radius and overall chamber shape can vary between castings. Heads that have already been machined can be different again. Think of each .001" removed from the head as removing a very thin circular layer of aluminum. A larger circle contains more material than a smaller circle, so the larger pocket loses more combustion-chamber volume for the same .001" cut. This is why using one universal rule such as “15 thousandths equals one CC” can be misleading. That may be a good approximation for a pocket near 2.250", but it would be significantly different on a head with a 2.750" or 3.000" effective diameter. A Simple Example: 36 CC to 32 CC Suppose you have a Mercury V6 head that measures 36 CC and you want to reduce it to approximately 32 CC. You need to remove about 4 CC of chamber volume. With a 2.250" effective pocket, the estimated cut is approximately .0614". With a 2.500" pocket, it drops to approximately .0497". A 2.750" pocket requires approximately .0411", while a 3.000" effective pocket calculates to approximately .0345". Pocket Diameter Approximate Cut for 4 CC 2.000" .0778" 2.250" .0614" 2.375" .0551" 2.500" .0497" 2.750" .0411" 3.000" .0345" This comparison demonstrates why measuring the pocket before machining is important. The desired CC reduction may be identical, but the required fly cut can be considerably different. Starting CC Is Not the Most Important Number Whether the head starts at 43 CC, 38 CC, 36 CC or 30 CC does not by itself determine how many thousandths need to be removed. What matters for this calculation is how many CCs you want to remove and the effective diameter of the area being machined. For example, reducing a 38 CC chamber to 34 CC is a 4 CC reduction. Going from 36 CC to 32 CC is also a 4 CC reduction, as is going from 34 CC to 30 CC. If the effective pocket diameter and chamber geometry are the same, all three require approximately the same amount of material removal. This makes the chart useful across a wide range of Mercury V6 cylinder-head volumes rather than limiting it to one starting CC. Chamber Depth and Shape Chamber depth affects the total volume of the combustion chamber, but it does not directly determine how many CCs are removed by each thousandth of a fly cut. The more important measurement is the effective diameter of the area being removed at that particular point in the chamber. The complication is that a Mercury combustion chamber is not a perfect straight-sided cylinder. Most chambers incorporate a squish area, radiused transitions and other contours. As a head is cut farther, the effective diameter can change as the machining reaches these features. This is where a mathematical chart has limits. The numbers are very useful while the effective cutting area remains reasonably close to the stated diameter. Once the cut begins changing the chamber geometry, the actual CC reduction may no longer follow the chart exactly. The Best Way to Use This Chart Start by accurately CC'ing the cylinder head and measuring the effective pocket diameter. Determine how much chamber volume you want to remove, then use the chart to estimate the required material removal. On an unfamiliar casting, it is better to make a conservative initial cut rather than attempting to reach the final chamber volume in one operation. CC the chamber again after that cut. You now know how much volume was actually removed from that particular head. For example, if you make a .030" cut and the chamber volume decreases by exactly 2 CC, you have established the real machining relationship for that cylinder head. That measured result is more valuable than any generic chart and can be used to calculate the remaining finishing cut much more accurately. As the chamber approaches the desired volume, smaller cuts and repeated CC measurements provide much better control. The chart should get you close; the burette tells you where you actually are. CC and Compression Reducing chamber volume generally increases compression, but the finished CC number should never be considered by itself. A Mercury V6 engine combination also depends on the cylinder-head casting, displacement, piston configuration, deck position, squish clearance, head-gasket thickness, port timing, ignition timing, fuel octane, carburetor or EFI calibration, cooling-system condition, RPM and engine load. A small-chamber cylinder head that works correctly on a purpose-built race engine using appropriate fuel may not be suitable for a recreational Mercury V6 operating on pump gasoline. Increasing compression can improve torque and throttle response, but it also reduces the engine's margin against detonation. The correct chamber volume is therefore determined by the complete engine combination—not simply by how far the head can physically be machined. Large Fly Cuts Require Additional Inspection The chart extends through a 10 CC reduction so that builders can compare different pocket diameters, but the larger numbers are mathematical references only. They do not establish that a particular Mercury head can safely have that amount of material removed. As machining becomes more aggressive, remaining head thickness, chamber and squish geometry, spark-plug location, water-jacket location, gasket sealing and piston-to-head clearance become increasingly important. If the chart calculates a very large cut, inspect and measure the actual cylinder head before proceeding. The calculation tells you approximately how much volume a cut removes; it does not determine whether that cut is mechanically appropriate for the head or engine. Buckshot Racing #77 Quick Shop Reference For approximately 1 CC of chamber-volume reduction, use 19.4 thousandths for a 2.000" pocket, 15.3 thousandths for a 2.250" pocket, 13.8 thousandths for a 2.375" pocket, 12.4 thousandths for a 2.500" pocket, 10.3 thousandths for a 2.750" pocket, and 8.6 thousandths for a 3.000" pocket. The easiest rule to remember is: Larger pocket = more CC removed per thousandth = less fly cut required per CC. The Burette Is the Final Word The Buckshot Racing #77 Mercury V6 fly-cut chart is designed to provide a practical starting reference for 2.0L, 2.4L and 2.5L two-stroke cylinder-head machining. Measure the pocket, accurately CC the chamber, use the chart to estimate the cut, and then measure the chamber again before making the final machining pass. Different Mercury cylinder-head castings and previously modified heads will vary. The chart gets you close. The actual CC measurement determines the finished head. Buckshot Racing #77 Mercury 2.0L • 2.4L • 2.5L V6 Two-Stroke Performance Performance Parts • Racing Components • Mercury V6 Technical Information This guide is intended as a general machining and educational reference. Always verify actual chamber dimensions, chamber volume, remaining material, piston-to-head clearance, compression, ignition timing, cooling and fuel requirements for the specific engine combination before operation.

Mercury 2-Wire Trim Motor Wiring, Relays & Troubleshooting | Buckshot Racing #77 Mercury outboard power trim and tilt systems allow the operator to change engine angle for acceleration, running attitude, shallow-water operation, and trailering. Many Mercury and Mercury Racing outboards use a 12-volt, permanent-magnet, 2-wire trim motor controlled by a pair of trim relays. Understanding this design is important because a 2-wire motor works differently from the older 3-wire trim-motor systems. There is no dedicated ground wire at the motor. Instead, the electrical system reverses polarity across the two motor leads to change the direction of the pump motor. Mercury service literature specifically identifies power-trim systems using relays and a 2-wire trim motor, and newer Mercury diagnostic documentation describes the relay system as connecting each motor wire to either battery positive or ground to run the motor in either direction. How a Mercury 2-Wire Trim Motor Works A permanent-magnet DC motor changes rotation when the polarity applied to it is reversed. In one direction, one motor lead receives battery positive while the other lead provides the negative return path. When the operator commands the opposite direction, the relay system reverses those connections. The electric motor then drives the hydraulic pump in the opposite direction. Mercury service documentation confirms that pressing DOWN runs the power-trim pump in the opposite direction from UP. This is the basic operating principle: UP: one motor lead becomes positive and the opposite motor lead becomes negative. DOWN: polarity across those same two leads is reversed. That is why a 2-wire trim motor does not have a permanently assigned positive lead and ground lead. Mercury Trim Motor and Trim-Switch Wire Colors On Mercury systems documented in factory service literature, blue is identified with trim motor UP and green with trim motor DOWN. Mercury also commonly uses blue/white for the trim-switch UP control circuit and green/white for the trim-switch DOWN control circuit. That distinction matters. The heavier blue and green motor conductors are part of the high-current reversing circuit. The blue/white and green/white switch wires, where used, are control-circuit conductors that energize the appropriate relay. Do not assume these colors apply to every Mercury outboard ever produced. Always verify the specific engine wiring diagram by model and serial number before repairing or modifying the circuit. How the Two Mercury Trim Relays Work A proper 2-wire Mercury trim system uses an UP relay and a DOWN relay. When neither relay is energized, Mercury documentation for permanent-magnet trim systems shows both motor leads connected to ground through the normally closed relay contacts. When UP is selected, the UP relay switches its motor lead from ground to battery positive. The DOWN relay remains at rest and provides ground for the opposite motor lead. When DOWN is selected, the opposite occurs: the DOWN relay supplies battery positive while the UP relay provides the ground return. Mercury's own troubleshooting information states that if the motor will not run in the UP direction, either the UP relay may not be supplying 12 volts or the DOWN relay may not be making the required ground connection. This is one of the most important diagnostic points in a Mercury 2-wire system: a relay can affect the opposite direction even when that relay is not the one being actively energized. Why Mercury Uses Relays A trim motor is a high-current electrical load. The helm, remote-control, or cowl trim switch is therefore not intended to carry the trim motor's full operating current directly. Instead, the operator's switch energizes the relay control circuit. The relay contacts then handle the higher-current path between the battery and the trim motor. This allows a relatively low-current trim switch to control a considerably larger DC motor reliably. Basic Mercury 2-Wire Trim Motor Bench Test Mercury's service procedure for a trim-pump motor test calls for a 12-volt power source connected directly to the two motor leads, with one lead connected to positive and the other connected to negative. Mercury also warns that a spark may occur while making these connections and says not to perform the test near flammable materials. For a reversible permanent-magnet motor, reversing those two connections reverses motor direction. For example, on an application where the motor leads are confirmed as blue and green: Test Blue lead Green lead Expected result Direction 1 +12 V Battery negative Motor runs one direction Direction 2 Battery negative +12 V Motor runs opposite direction Use this only after confirming the wiring for the particular motor. The test battery should be fully charged, and the leads and connections need enough current-carrying capacity for the trim motor. Mercury's troubleshooting procedures specifically call for making sure the battery is fully charged and electrical connections are tight and corrosion-free. Important Bench-Test Safety A trim motor can draw substantial current. A poor jumper lead, undersized conductor, loose clamp, corroded terminal, or weak battery can create enough resistance to make a perfectly good motor appear defective. Direct battery connections can also spark. Keep testing away from gasoline, fuel vapor, solvents, batteries being charged, or other flammable material. If testing the complete trim-and-tilt assembly rather than a loose electric motor, keep hands, tools, and wiring clear of moving components and pinch points. When working around a raised outboard, mechanically support it according to the Mercury service procedure; do not depend solely on hydraulic pressure to hold the engine up. Mercury service instructions specifically call for engaging the tilt lock or otherwise supporting the outboard during trim-system service. Why a Motor Can Work on the Boat but Fail on a Bench Test Battery voltage by itself does not prove the test circuit can supply adequate current. A battery might measure more than 12 volts with no load and still have poor capacity. Likewise, a small test wire may show full battery voltage on a multimeter but develop a large voltage drop as soon as the trim motor starts drawing current. If an installed motor operates normally but will not operate during a bench test, check the test equipment before condemning the motor. Pay particular attention to conductor size, battery condition, clamp contact, terminal cleanliness, and voltage measured while the motor is actually running. Motor Works in One Direction Only A 2-wire motor that operates normally in one direction is an important diagnostic clue. Because the same armature and the same two motor leads are used for both directions, a failure in only UP or only DOWN frequently points toward the relay circuit, switch circuit, connector, or wiring rather than the motor itself. Mercury service documentation confirms this relationship. An UP failure can result from either the UP relay failing to supply positive voltage or the DOWN relay failing to provide the required ground path. Do not automatically replace the relay whose name matches the failed direction without testing both sides of the reversing circuit. Relay Clicks but the Trim Motor Does Not Run A relay clicking only proves that the electromagnetic coil is moving the relay mechanism. It does not prove that the high-current contacts are carrying adequate current. Internal relay contacts can become resistive, burned, or corroded. That is why voltage testing should be performed while the system is under load whenever possible. Mercury troubleshooting procedures use voltage measurements throughout the UP and DOWN circuits rather than relying on relay noise alone. Both UP and DOWN Are Dead If neither direction operates, begin with the common portions of the circuit. Mercury's troubleshooting sequence starts with basic checks including disconnected wiring, tight and corrosion-free connections, fully engaged connectors, battery condition, and the system fuse. Factory troubleshooting for an all-circuits-inoperative condition specifically directs the technician to inspect the inline fuse. A failure affecting both directions is more likely to involve a common power supply, fuse, ground path, connector, control-feed circuit, battery connection, or multiple-relay issue than a single UP/DOWN switch output. Motor Runs but the Engine Does Not Move Once the trim motor can be heard operating normally, separate the electrical diagnosis from the hydraulic diagnosis. Mercury service literature specifically instructs technicians to first determine whether a trim problem is electrical or hydraulic. If the motor runs but the engine does not rise or lower correctly, investigate hydraulic-fluid level, air in the system, the manual-release valve, pump operation, internal leakage, seals, check valves, and other hydraulic components according to the appropriate Mercury service manual. Do not continue replacing electrical components when the electric motor is operating normally and the actual failure is hydraulic. Do Not Run a Dry Trim Pump Continuously When an assembled trim pump has been opened, drained, or repaired, avoid prolonged motor operation before the hydraulic system is properly filled and primed. Mercury service literature instructs technicians to run the trim system in short jogs until the pump is primed and the trim system begins moving. That is a much better practice than continuously running an unprimed pump assembly. Replacing a Mercury 2-Wire Trim Motor Do not select a replacement solely because it has two wires. Confirm the exact Mercury application, mounting pattern, shaft or pump interface, motor lead connections, hydraulic-pump design, sealing arrangement, and service part number. Mercury and Quicksilver replacement trim motors are application-specific, and Mercury repeatedly advises verifying the particular owner's or service manual for installation information. Whenever possible, identify the engine by serial number before ordering trim-system parts. Buckshot Racing #77 Technical Summary A Mercury 2-wire trim motor is a reversible permanent-magnet DC motor. Direction is controlled by reversing polarity across the two motor leads. The factory system normally accomplishes that with two relays: one UP relay and one DOWN relay. For documented Mercury systems, blue is associated with motor UP, green with motor DOWN, blue/white with the UP control circuit, and green/white with the DOWN control circuit—but the serial-number-specific Mercury diagram should always be verified before service. When troubleshooting, remember the core principle: Two motor wires. Two reversing relays. Each direction requires both a positive path and a ground path.

Installing an Electronic Power Steering (EPS) system can transform the handling of your high-performance race boat by delivering responsive, effortless steering control under high G-loads, rough water, and aggressive cornering. Whether you're racing in US F1, F1H2O, or any high-speed competition class using a traditional cable and pulley steering system, this guide will walk you through the professional installation of your EPS kit and help you choose the right model for your setup. Choosing the Right EPS System for Your Boat The EPS system comes in three powerful configurations to match the specific demands of various racing engine classes. Each model is designed to enhance boat control, reduce driver fatigue, and improve overall performance under race conditions. The 220-Watt (220W) EPS system is best suited for lightweight, lower-horsepower race boats equipped with engines up to 125 HP. This includes popular models such as the OMC SST-45, SST-60, and Yamaha 3-cylinder outboards. This system delivers reliable electronic assist during sharp turns, rough water runs, and "on-the-pad" balance where fine adjustments are critical. If you’re running a smaller, nimble hull in competitive classes, the 220W is a perfect match. The 400-Watt (400W) EPS system offers increased power for mid-range high-revving racing engines. This version is ideal for boats powered by Mercury Racing 2.5L, S3000, SST-120, F1, F2, Optimax SST-200XS, 300 Drag, or OMC V6 2-Stroke engines. It strikes the perfect balance between assist force and steering feedback, making it ideal for competitive drivers who require tight cornering, fast recovery from chine walk, and superior tracking through rough conditions. The 600-Watt (600W) EPS system delivers torque and steering assistance. Designed to manage the steering loads from Mercury APX 200 HP, 250 HP, and 360 HP 4-Stroke engines, or even classic OMC V8 2-Strokes, the 600W model ensures stable, responsive steering at any speed. This system is ideal for circle boat setups or heavy-duty race applications where power steering is a critical safety and performance factor. The 700-Watt (700W) EPS system delivers maximum torque and steering assistance. Designed to manage the steering loads from Mercury APX 200 HP, 250 HP, and 360 HP 4-Stroke engines, or even classic OMC V8 2-Strokes, the 700W model ensures stable, responsive steering at any speed. This system is ideal for circle boat setups or heavy-duty race applications where power steering is a critical safety and performance factor. Preparation for Installation Before beginning installation, it’s essential to download and review the full instruction manual that includes wiring diagrams and installation illustrations. Check all electrical connectors to ensure that rubber gaskets are fully seated to prevent moisture intrusion. If needed, gently press them in using a flathead screwdriver. Make sure your existing steering cable and pulley system is in good condition, as the EPS is designed to supplement, not replace, mechanical components. ECU Mounting Choose a secure and protected area within the cockpit or hull compartment to mount the Electronic Control Unit (ECU). This location should offer easy access for future diagnostics while remaining isolated from water spray or vibration-prone surfaces. Using the provided M8 hardware, fasten the ECU securely. Ensure the unit is oriented properly to avoid wire stress and interference. Motor and Mount Installation Next, prepare the motor mounting system. The EPS motor must be mounted firmly to absorb torque without flexing. The provided mount may need minor modifications to fit your hull or steering tray configuration. Once aligned, secure the motor to the mount using the M10 screws. Tighten the hardware evenly to prevent binding or misalignment. Steering Shaft Installation The EPS kit includes two steering shafts, which serve as the mechanical link between the motor and your cable system. Adjust the shaft lengths and angles to ensure smooth operation, avoiding tight bends or misalignment with the existing pulleys. Once fitted correctly, secure the shafts to the motor using the supplied hardware. Check for free movement throughout the entire steering range before proceeding. Wiring the EPS System With the mechanical components in place, it’s time to wire the system. Connect the EPS motor to the ECU using the supplied wiring harness. Each wire is color-coded for easy reference: Red wire connects to the battery positive (+) Black wire connects to the battery negative (-) White wire activates the LED diagnostic light A separate line connects to a switched 12V ignition source Route and secure all wiring using zip ties and protective loom. Avoid routing wires near hot engine parts or sharp edges. Coil and secure any unused wires, such as a blue wire on some models, in a dry location. System Activation and Diagnostic Test With everything connected, turn the ignition key to activate the system. The EPS unit should power on, and the diagnostic LED will flash once for about one second before turning off. This indicates proper system operation. If you observe different flashing patterns or no light at all, refer to the diagnostic codes provided in your kit manual. Final Checks and Compliance Before hitting the water, double-check all hardware connections and wire routing. Make sure nothing is loose or exposed. Retain the original packaging until installation is fully confirmed. This EPS system is engineered for performance marine use and should be installed by experienced technicians. Always ensure your setup complies with local, state, and federal boating regulations. Any modification to this EPS kit outside of recommended configurations may void your warranty and could compromise safety or legality. If you need additional support or want to view the full illustrated manual, download it below or contact Mike@BuckshotRacing77.com or +1-714-697-1716. This guide will help ensure your Electronic Power Steering system is correctly installed for peak performance, safety, and control in any racing environment. Download the PDF installation guide below! 220, 400, 600 Watt System Instructions 700 Watt EPS System Instructions

Buckshot Racing 77 350-HSTEER hydraulic steering kit for high-performance outboard boats. Includes cylinder, helm pump, fittings, tubing, hardware, and hydraulic oil. The Buckshot Racing #77 350 HP and 700 HP Hydraulic Steering Kits are built for outboard owners, racers, performance boat builders, and marine installers who need strong, smooth, dependable steering control. A hydraulic steering system replaces mechanical cable steering with a helm pump, hydraulic hoses, and one or more steering cylinders. When the steering wheel is turned, the helm pump moves hydraulic oil through the hoses and shifts the steering cylinder, which moves the outboard from port to starboard. Correct installation is critical. Hydraulic steering controls the direction of the boat, so every fitting, hose, cylinder fastener, helm mount, bleed screw, spacer, washer, and steering connection must be installed correctly. This Buckshot Racing #77 tech guide explains the major installation points for both the 350 HP and 700 HP hydraulic steering systems. 350 HP Hydraulic Steering Kit Overview The 350 HP hydraulic steering kit is commonly used for single outboard applications where one helm pump controls one front-mount steering cylinder. This setup is ideal for many performance boats, bass boats, flats boats, lake boats, fishing boats, and single-engine outboard rigs that need clean, reliable hydraulic steering with reduced steering effort. The system uses a helm pump, steering cylinder, hydraulic hoses, fittings, fluid, and mounting hardware. The steering cylinder mounts at the engine tilt tube area and connects to the engine steering arm. Before final assembly, the cylinder should be centered, the engine should be positioned straight, and the steering arm should be square to the transom. 700 HP Hydraulic Steering Kit Overview The 700 HP hydraulic steering kit should be understood as the higher-capacity steering option. It may be used on applications where horsepower, hull speed, engine torque, steering load, setback, surfacing propeller operation, or race use requires additional steering capacity and control. Twin-engine applications are one common reason to use a higher-capacity steering system, but the correct kit should always be selected based on the actual boat setup, horsepower, steering load, engine configuration, cylinder arrangement, and intended use. High-performance single-engine boats can also create serious steering loads, especially with high horsepower, large setback, elevated engine height, and surfacing props. Before Installation Before installing any hydraulic steering kit, confirm that the system matches the engine horsepower, engine count, transom layout, splashwell clearance, cylinder style, hose length, helm pump, and steering load. Inspect the boat before drilling or mounting anything. The dash must have enough room for the helm pump and fittings, and the splashwell must allow the engine to steer fully and tilt fully without the cylinder, hoses, fittings, or hardware contacting the boat. Helm Pump Installation The helm pump mounts at the dash and becomes the control unit for the steering system. Cut the dash opening to the required size, mark and drill the mounting holes, install the helm pump into the panel, and secure it with the supplied mounting hardware. The steering wheel should only be installed after confirming that the wheel fits the helm shaft, keyway, and taper correctly. Hydraulic fittings must be installed cleanly and tightened properly. Do not cross-thread, over-tighten, or contaminate hydraulic fittings. If thread sealant is required, use the correct type and keep sealant out of the hydraulic system. Steering Cylinder Installation The steering cylinder mounts at the outboard tilt tube and steering arm area. Start by centering the cylinder rod and positioning the engine straight. The support rod should be greased with marine grease before installation to help prevent corrosion. The cylinder plate connects to the engine steering arm using the correct bolt, washer, and locking hardware. Correct spacing is critical. The washers, spacer rings, support rod, adjustment nut, and steering arms must be installed so the cylinder is not side-loaded or binding. The steering should move evenly from side to side, and the engine should reach full travel without interference. Hose Routing Hydraulic hoses must be routed cleanly with no kinks, twists, sharp bends, stretching, or rubbing. Keep hoses away from steering linkage, jack plates, cowling edges, exhaust heat, sharp fiberglass, and moving parts. Leave enough service loop for full steering and full engine tilt movement, but do not leave hoses loose where they can chafe or whip. On higher-capacity 700 HP installations, hose routing and clearance checks are even more important because the steering system may be exposed to heavier loads and more aggressive boat movement. Filling and Bleeding Hydraulic steering must be filled and bled completely before use. The system should be filled with the specified hydraulic fluid, and the helm reservoir must be kept full during bleeding. Turn the steering wheel slowly while opening the bleeders in sequence until a clean, steady stream of air-free oil comes out. Do not spin the steering wheel quickly during bleeding. Turning the wheel too fast can foam the oil, trap air in the system, and create spongy or inconsistent steering. If the oil becomes foamy, allow the system to sit before continuing. Post-Installation Testing After installation and bleeding, inspect the helm, hoses, fittings, cylinder, bleeders, and connections for leaks. Turn the wheel from full port to full starboard and verify smooth steering in both directions. Count wheel turns both ways and confirm that steering travel is even. Tilt the engine through its full range and check for interference. The cylinder, hoses, fittings, support rod, steering arms, and related hardware must not contact the transom, splashwell, jack plate, cowling, or rigging. If anything touches, binds, stretches, or interferes, stop and correct the installation before operating the boat. Maintenance and Safety Checks Hydraulic steering should be inspected regularly. Check for leaks, loose fittings, damaged hoses, steering play, corrosion, worn hardware, low fluid level, and changes in steering feel. Keep exposed steering hardware clean and lubricated where appropriate. Any sudden change in steering effort, wheel response, fluid level, or engine movement should be inspected immediately. Never operate the boat with visible steering leaks, kinked hoses, loose hardware, air in the system, damaged fittings, or steering interference. Hydraulic steering is a critical safety system. If the installer is not experienced with marine hydraulic steering, the installation should be nspected by a qualified marine technician. Buckshot Racing #77 Final Tech Note The Buckshot Racing #77 350 HP and 700 HP Hydraulic Steering Kits are designed to deliver strong, clean, high-performance steering control when installed correctly. The 350 HP kit is a proven choice for many single-engine applications, while the 700 HP kit is the higher-capacity option for heavier steering loads, higher horsepower, more aggressive setups, and demanding performance use. Take the time to measure carefully, route hoses correctly, bleed the system fully, and verify full steering and tilt movement before running the boat. Download the PDF Instruction Guide Here:

Learn how to install a Mercury DTS foot throttle, including 9.5-inch pedal radius, 30° travel, mounting holes, adapter harness wiring, and Mercury Racing 8M0245913 setup. A Mercury Digital Throttle & Shift (DTS) foot throttle gives performance-boat drivers the ability to control engine speed with their foot while keeping both hands on the steering wheel. Unlike a traditional mechanical Hot Foot that pulls a throttle cable, the Mercury DTS pedal sends an electronic throttle-demand signal through the boat’s DTS control system. Mercury specifically notes that this arrangement is useful on boats capable of significant speed because it allows the operator to maintain two-handed steering control. For performance bass boats, single-engine catamarans, tunnel-style boats, and other high-performance Mercury-powered applications, proper installation is just as important as the pedal itself. The pedal must have enough room to travel through its full range without contacting the deck, bulkhead, or the driver’s shoe, and the harness must be routed and supported correctly. This Buckshot Racing #77 Tech Hub guide covers the factory Mercury DTS foot throttle mounting dimensions, installation procedure and legacy DTS adapter-harness architecture, along with practical installation considerations for the Mercury Racing 8M0245913 DTS Performance Foot Throttle Pedal. DTS Foot Throttle Mounting Location and Clearance Before drilling any holes, sit in the boat in the normal driving position and determine where your foot naturally rests. The goal is not simply to find a location where the pedal physically fits. The driver must be able to operate the throttle smoothly from idle through wide-open throttle without stretching, lifting the heel excessively, or allowing the shoe to contact surrounding structure. Mercury specifies a 241 mm (9.5-inch) pedal radius and a maximum pedal travel of 30 degrees. Additional clearance must also be provided beyond the pedal's travel arc for the driver's shoe. This shoe-clearance requirement is important. A pedal can appear to have adequate clearance when moved by hand yet interfere once a driver's foot is actually on it. Check the complete travel arc with the intended driver seated normally and wearing the type of footwear normally used in the boat. The pedal should also return freely to idle from every position. Nothing in the cockpit—carpet, wiring, trim panels, loose equipment, or the driver's shoe—should restrict its movement. Mercury DTS Foot Throttle Installation Guide: Mounting, Clearance & Adapter Harness Setup Installing the Mercury DTS Foot Throttle Once a comfortable mounting position has been established, route the pedal wiring so you know the harness can reach the appropriate connection without being stretched. Mercury's installation procedure then calls for using the foot-pedal base as the drilling template. Mark the mounting holes directly from the base and drill five 4 mm (5/32-inch) holes. The pedal is secured to the deck with #12 screws and washers, which are not supplied with the installation kit. After mounting the pedal, connect the harness assembly to the helm harness. Any excess wiring should be coiled neatly and secured with a cable tie rather than stuffed loosely behind the pedal or dash. Mercury also specifies securing the harness to the boat structure with cable ties or D-clamps. Pay particular attention to areas where the harness passes around steering components, moving pedal hardware, or sharp fiberglass and aluminum edges. The harness should have enough slack for its intended routing but should not be able to fall into moving components. Finally, install the foot-throttle mounting-plate cover and secure it with the two supplied screws. Wiring and system configuration should follow the applicable Mercury rigging manual for the specific DTS installation. Understanding the Legacy DTS Foot Throttle Adapter Harness On a legacy Mercury DTS installation, the foot-throttle system is more than simply a pedal plugged into an engine harness. The factory architecture can include the Legacy Control Module (LCM), foot-throttle adapter harness, foot throttle, junction box, weather caps, foot-throttle ON/OFF switch, and helm harness. The adapter-harness diagram identifies four primary connections: 1 — Legacy Control Module (LCM), 2 — throttle ON/OFF, 3 — foot throttle, and 4 — junction box. Unused junction-box ports should remain properly protected with the appropriate weather caps. Do not leave an unused DTS connection exposed in a marine environment. This architecture is also why a DTS pedal should not be treated as a universal electronic Hot Foot. Mercury DTS rigging has changed through different generations, so the existing helm, engine, junction box, and harness configuration should be identified before ordering components or modifying the boat. mercury-dts-foot-throttle-installation • mercury-racing-8m0245913-foot-throttle • mercury-dts-performance-pedal-install • mercury-dts-foot-throttle-mounting-clearance • mercury-dts-foot-throttle-adapter-harness • mercury-dts-legacy-control-module-lcm • mercury-dts-foot-throttle-wiring-diagram • mercury-dts-hot-foot-installation-guide • mercury-racing-digital-foot-throttle-pedal • mercury-dts-junction-box-foot-throttle • mercury-dts-hand-foot-throttle-switch • mercury-performance-boat-dts-rigging Hand Throttle vs. Foot Throttle Operation One of the advantages of the factory DTS arrangement is that compatible systems can retain both hand and foot throttle control. Mercury's operating instructions state that you can control engine speed from idle through wide-open throttle using either the foot throttle or the panel-mounted control handle. At startup, the foot throttle is the default throttle input in the system described by Mercury. To transfer control to the hand throttle, the remote-control handle must be placed in neutral or the forward/reverse detent position before the hand-throttle ON/OFF switch is pressed. The system then provides a horn confirmation and illuminates the hand-throttle indicator. That functionality can be especially useful on a performance boat. The driver can use the hand control for docking and low-speed maneuvering, then select the foot throttle when conditions call for two-handed steering control. Always verify operation according to the manual for the specific engine and DTS generation rather than assuming every Mercury DTS installation functions identically. Mercury Racing 8M0245913 DTS Performance Pedal The current Mercury Racing OEM 8M0245913 DTS Performance Foot Throttle Pedal is designed specifically as an electronic throttle input for compatible Mercury DTS installations. It is not a mechanical pedal and does not operate a Gen I, Gen II or 33C throttle cable. The 8M0245913 uses an anodized billet-aluminum pedal assembly with a non-slip pad and toe hook. Its compact electronic sensor is substantially smaller than the earlier design while retaining the existing harness architecture, which can simplify installation in tight performance-boat cockpits and upgrades of compatible legacy DTS systems. Because compatibility depends on the complete DTS rigging configuration rather than horsepower alone, verify the engine, control generation and existing harness architecture before purchasing. Mercury Racing 8M0245913 DTS Performance Foot Throttle at Buckshot Racing #77 Final Installation and Safety Check Before launching the boat, inspect the complete installation. Confirm that the pedal is firmly mounted, all electrical connectors are fully seated, unused ports are protected, and the harness cannot contact sharp edges or moving components. With the engine safely off, move the pedal through its complete travel and verify that the driver's shoe has adequate clearance throughout the 30-degree maximum pedal travel. Check that the pedal moves smoothly and returns without interference. Once the system is powered, verify correct throttle-selection operation and make sure the system recognizes the intended control before operating the boat. Initial functional testing should be performed in a controlled environment before any high-speed operation. A DTS foot throttle is ultimately a driver-control system, so mounting position, ergonomics, electrical integrity, and correct system configuration all matter. Taking extra time during installation can make the finished setup cleaner, easier to drive, and safer to operate. Mercury DTS Foot Throttle Parts Guide Choosing the correct Mercury DTS foot-throttle components depends on what is already installed in the boat. The performance pedal, pedal-and-harness kit, and helm kit are separate products and should not be confused with one another. Mercury Racing DTS Performance Foot Throttle Pedal — 8M0245913 Mercury Racing 8M0245913 is the current DTS Performance Foot Throttle Pedal. This is the pedal only and is intended for boats that already have the correct Mercury DTS foot-throttle wiring, control module, selector switch, and related helm-side components installed. Use 8M0245913 when replacing or upgrading the pedal on an existing compatible Mercury DTS foot-throttle system. Mercury Racing DTS Performance Foot Throttle Pedal & Harness Kit — 8M0245912 Mercury Racing 8M0245912 is the DTS Performance Foot Throttle Pedal Kit with harness components. This is the preferred package when the installation requires both the performance foot throttle pedal and its associated harness kit. Use 8M0245912 when installing the performance pedal into an application that does not already have the required pedal-side harness components. Mercury DTS Foot Throttle Helm Kit — 8M0169383 Mercury 8M0169383 is the DTS Foot Throttle Helm Kit. This is the helm-side portion of the system and is separate from the performance pedal itself. The kit provides the control and harness components required to integrate foot-throttle operation into compatible Mercury DTS rigging. Depending on the existing DTS configuration, the helm system can incorporate the Legacy Control Module (LCM), hand/foot throttle selector switch, adapter harness, junction-box connections, mounting components, and associated wiring. Use 8M0169383 when the boat requires the helm-side DTS foot-throttle controls rather than simply replacing the pedal. Additional Legacy DTS Components Mercury 893359K01 is a legacy DTS Hot Foot / Foot Throttle Harness Kit used in certain Mercury DTS foot-throttle installations. Mercury 898259K01 is the legacy Hand Throttle ON/OFF Switch Kit used on applicable DTS systems. It should not be confused with the foot throttle pedal or described simply as a foot-throttle switch. Which Mercury DTS Foot Throttle Kit Do I Need? If your boat already has the correct Mercury DTS foot-throttle architecture and you only need the new performance pedal, order 8M0245913. If you need the performance pedal together with the pedal-side harness kit, order 8M0245912. If the boat also requires the helm-side control module, selector controls, and associated DTS foot-throttle wiring, the installation may require 8M0169383 and other applicable Mercury DTS rigging components. Because Mercury DTS systems have been produced in several generations and configurations, always identify the existing engine, helm controls, DTS generation, junction box, control module, and harness arrangement before ordering parts. Do not assume that the pedal alone will convert a standard DTS boat to foot-throttle operation. Buckshot Racing #77 recommends verifying the complete DTS architecture before installation so the correct pedal, harness, and helm components are ordered the first time.