Mercury Outboard Parts Lookup & Cross-Reference | Buckshot Racing #77 Find the Right Parts. Build More Power. Stay Race Ready. Looking for high-performance outboard racing parts? Buckshot Racing #77 specializes in Mercury Racing and performance outboard components for both two-stroke and four-stroke engines. From pistons, rod bearings, reed cages, carburetors, EFI components, and ignition systems to lower units, propellers, steering, and race boat safety equipment, we help racers and performance boating enthusiasts find the parts they need. Search Our Outboard Racing Parts Catalog Use the Parts Finder below to search by part name, OEM part number, or engine model. Enter terms such as "2.5 piston," "17514A1," "4-stroke ECU," or "prop" to see matching products, current listed prices, and direct links to purchase. Can't find a match? Expand your search to our entire Speed Store with one click. Hard-to-Find Parts? Ask Mike. Finding the right racing component isn't always straightforward. OEM part numbers change, older components become discontinued, and proper fitment is critical. If your search comes up empty, use the "Ask Mike" feature for personalized parts assistance. We'll help identify components, research OEM cross-references, and locate available replacements or performance upgrades. Whether you're rebuilding a Mercury 2.0L, 2.4L, or 2.5L V6, maintaining a 3.0L performance outboard, tuning a modern four-stroke, or outfitting your race boat, Buckshot Racing #77 delivers the parts knowledge and support you need. Our growing catalog includes engine internals, fuel and ignition systems, gaskets, powerhead components, lower units, propellers, steering hardware, and racing accessories, with worldwide shipping available. Need Help Finding a Part? Call or Text: 714-697-1716 Email: mike@buckshotracing77.com Include your engine model, serial number, OEM part number, and any available photos. Boat information can also help us confirm compatibility. We'll research your request and follow up with available options, fitment information, and pricing. BUCKSHOT RACING #77 — Built by Racers. Backed by Experience.

Buckshot Racing #77 100 MPH Club propeller speed chart showing 28 combinations of prop pitch, lower-unit gear ratios, and required RPM at 10% slip for high-performance outboards. How to Choose the Right Prop Pitch, Gear Ratio & RPM to Reach 100 MPH Breaking the 100 MPH barrier with an outboard-powered boat requires the right combination of horsepower, lower-unit gear ratio, propeller pitch, engine RPM, and hull setup. Whether you're running a Mercury, Yamaha, Suzuki, Evinrude, or another high-performance outboard, understanding how these factors work together is essential. The Buckshot Racing #77 Prop Speed Calculator helps boat owners estimate speed, evaluate propeller pitch, compare gear ratios, and determine the RPM required to reach their performance goals. From bass boats and V-bottoms to STVs, HydroStreams, tunnel hulls, and offshore performance boats, the basic principles remain the same. Reaching 100 MPH isn't just about horsepower. It's about turning that horsepower into efficient forward speed. Understanding Gear Ratio, Prop Pitch & RPM Three primary numbers determine theoretical propeller speed. Gear Ratio: Your lower-unit gear ratio determines how many engine revolutions produce one propeller revolution. For example, a 1.50:1 gearcase turns the propeller once for every 1.5 engine revolutions. A 1.87:1 gearcase turns the propeller slower at the same engine RPM. Propeller Pitch: Pitch represents the theoretical forward distance a propeller travels in one revolution, measured in inches. Higher pitch provides greater potential speed but increases engine loading. Lower pitch generally improves acceleration and allows the engine to achieve higher RPM. Engine RPM: Wide-open-throttle (WOT) RPM determines how quickly the propeller rotates through the gearcase. Selecting the appropriate pitch helps keep your engine within its intended operating range. These three values establish theoretical speed. Actual performance depends on propeller slip, available horsepower, and boat setup. What Is Propeller Slip? A propeller does not travel through water exactly as far as its advertised pitch suggests. The difference between theoretical and actual forward travel is called propeller slip. The Buckshot Racing #77 Calculator uses 10% slip as a practical starting point for estimating performance. Actual slip varies with hull design, engine height, trim, propeller geometry, boat weight, water conditions, and overall setup. A well-developed performance boat may operate below 10%, while other applications experience significantly more. Understanding your actual slip helps identify whether changes in propeller pitch, engine height, or setup are improving efficiency. How the Prop Speed Calculator Works The calculator estimates boat speed using your engine RPM, propeller pitch, lower-unit gear ratio, and an assumed 10% slip. The basic formula is: MPH = (RPM × Pitch × 0.90) ÷ (Gear Ratio × 1,056) For example, an outboard turning a 30-inch pitch propeller at 6,400 RPM through a 1.62:1 gearcase produces approximately 101 MPH at 10% slip. The calculator also works backward, showing the engine RPM required to achieve a selected target speed with different propeller pitches and gear ratios. Set your goal to 100 MPH, compare the combinations, and identify which ones fall within your engine's safe operating range. Remember, the calculator estimates mathematical speed. It cannot determine whether your engine produces sufficient horsepower to turn the selected propeller under actual operating conditions. Choosing the Right Propeller for 100 MPH There is no single propeller that will make every outboard-powered boat reach 100 MPH. A lightweight tunnel hull with a high-revving Mercury two-stroke may require a completely different combination than a modern four-stroke-powered performance boat. Begin by identifying your lower-unit gear ratio and the manufacturer's recommended WOT RPM range. Next, use the calculator to compare the pitch and RPM combinations required for your target speed. Higher pitch does not automatically produce higher boat speed. If the propeller overloads the engine, RPM may decrease enough to reduce overall performance. Likewise, excessive RPM with insufficient pitch may prevent the boat from reaching its full potential. The objective is to select a propeller that allows the engine to operate within its appropriate RPM range while efficiently carrying the boat. How Much Does One Inch of Prop Pitch Change RPM? A common starting guideline is that increasing propeller pitch by one inch may reduce WOT RPM by approximately 150–200 RPM, while reducing pitch may increase RPM by a similar amount. Actual results vary substantially with engine torque, propeller diameter, blade count, cup, rake, and hull characteristics. This guideline is useful for initial comparisons, but it is not a guaranteed conversion. Two propellers with identical advertised pitch can deliver very different acceleration, slip, and maximum speed. Calculate Your Actual Propeller Slip If you know your GPS speed, engine RPM, propeller pitch, and gear ratio, you can calculate estimated propeller slip. First determine theoretical speed: Theoretical MPH = (RPM × Pitch) ÷ (Gear Ratio × 1,056) Then: Slip = 1 − (GPS MPH ÷ Theoretical MPH) For example, a 1.62:1 gearcase turning a 30-inch pitch propeller at 6,200 RPM produces approximately 108.7 theoretical MPH. If your actual GPS speed is 94 MPH, calculated slip is approximately 13.5%. Use this information to establish a baseline before making additional changes. Beyond the Calculator: What Makes a 100 MPH Boat? The correct propeller combination is only part of the equation. Hull weight, running surface, aerodynamic lift, engine mounting height, trim angle, gearcase drag, propeller design, and available horsepower all influence maximum speed. Propeller blade geometry, rake, cup, and diameter also affect how efficiently the boat accelerates, maintains grip, and carries its load. A propeller with the highest theoretical speed is not necessarily the fastest propeller on the water. The right combination balances horsepower, RPM, propeller efficiency, and hull performance. Buckshot Racing #77 Performance Tips For meaningful propeller comparisons, record your GPS speed, engine RPM, propeller specifications, gear ratio, engine height, trim setting, fuel load, and operating conditions. Keep loading consistent between tests and change only one setup variable at a time. Always verify tachometer accuracy and the actual lower-unit gear ratio before interpreting calculated slip. If your engine cannot reach its recommended WOT range, investigate excessive propeller loading and other mechanical or setup issues before increasing pitch. For boats approaching triple-digit speeds, steering integrity, hull stability, engine mounting, gearcase condition, protective equipment, and driver experience become increasingly important. Never exceed manufacturer RPM limitations or the vessel's safe operating capabilities. Safety, Liability & Hold Harmless Disclaimer The Buckshot Racing #77 Prop Speed Calculator and accompanying technical information are provided for general educational and informational purposes only. All calculations are theoretical estimates and do not guarantee actual speed, performance, equipment compatibility, or safe operation. High-speed boating involves significant risks, including serious injury, death, and property damage. Users are solely responsible for evaluating their vessel, engine, propeller, equipment, operating conditions, and personal ability before making modifications or operating at elevated speeds. To the fullest extent permitted by applicable law, users agree not to hold Buckshot Racing #77 LLC, its owners, employees, or representatives liable for losses, injuries, damages, or claims arising from their use of the calculator or reliance on this information, except where liability cannot legally be excluded. Always follow manufacturer specifications, applicable boating laws, and recognized safety practices. Consult qualified marine performance professionals before attempting high-speed operation. Use of this information is at your own risk!

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.