API Marine WH476 Trim & Tilt Relay Harness — two-relay conversion harness for installing compatible two-wire trim motors on select older Mercury, Mariner, and Yamaha three-wire trim systems. Available from Buckshot Racing #77. The Buckshot Racing #77 Trim & Tilt Relay Harness by API Marine, Part Number WH476, is designed to install a compatible two-wire trim motor in place of an older three-wire motor. It includes the relays and color-coded wiring needed to reverse motor polarity for trim-up and trim-down operation. A traditional three-wire trim motor commonly uses separate blue and green leads for the up and down windings, with the motor grounded through a third wire. A two-wire motor changes direction by reversing polarity across its blue and green leads. The WH476 harness uses two relays to perform this polarity reversal when the trim switch is activated. API Marine specifies the WH476 for converting compatible Mercury and Yamaha three-wire systems to two-wire operation. It is intended for use with API Marine trim motors including PT-475TN-4, PT-476NMK-3, PT-485NMK-3, PT-495NK-3, PT608NK, PT609NK, and PT612NK. API Marine also states that these two-wire replacement motors have a lower amperage draw than the corresponding original three-wire motors. Complete Two-Relay Harness The WH476 is supplied as a prewired assembly, reducing the need to fabricate a relay circuit from separate components. Its color-coded connections simplify installation: Solid blue: two-wire trim motor blue lead Solid green: two-wire trim motor green lead Blue/white: trim-up control circuit Green/white: trim-down control circuit Red: fused positive battery supply When the trim-up switch is pressed, the relays apply voltage and ground in one direction. Pressing trim-down reverses polarity, causing the motor to rotate in the opposite direction. The harness includes two replaceable relays and inline circuit protection. Confirm the fuse rating supplied with the exact harness before replacing it; never install a fuse larger than the manufacturer-specified rating. Mercury and Mariner Applications The WH476 is commonly used when replacing an older round Prestolite or square Eaton three-wire trim motor with a compatible API Marine two-wire motor on select Mercury and Mariner integral trim-and-tilt systems. Applications may include certain 35 through 225 HP Mercury and Mariner outboards, including select inline engines and 2.0L, 2.4L, and 2.5L V6 two-strokes. Fitment is determined by the trim-system design and replacement motor—not horsepower or displacement alone. Verify all of the following before ordering: Original trim motor uses a three-wire connection Replacement trim motor uses a two-wire connection Trim pump and mounting pattern match the selected motor Harness connectors match the engine control wiring Relay mounting location matches the engine configuration Do not assume that every Mercury 2.0L, 2.4L, 2.5L, or 3.0L powerhead uses the same trim system. Engines with single-ram, three-ram, side-fill, aft-fill, remote-pump, or later factory two-wire systems may require different components. Important Part-Number Clarification Mercury numbers 882751A1 through 882751A9 identify various trim-relay assemblies or kits; they should not automatically be treated as direct cross-references for the complete WH476 conversion harness. Mercury 882751A1, for example, is cataloged as a trim relay assembly. The correct conversion harness should be selected according to the existing trim system and the API Marine two-wire motor being installed. For many older Mercury three-ram applications, another commonly listed conversion harness is Mercury 84-819514A15, which is associated with specific 1985–1992 side-fill systems and a different 30-amp harness configuration. Cross-reference numbers must therefore be verified individually rather than grouped together solely because they relate to trim relays. Installation Overview Disconnect the negative battery cable before beginning. Support the outboard securely and keep all wiring clear of the clamp bracket and other moving components. Connect the replacement motor’s solid blue and green wires to the matching blue and green harness leads. Connect the harness blue/white and green/white wires to the engine’s matching trim-control wires. Route the red power lead to a constant positive battery connection, normally the battery-side terminal of the starter solenoid or another manufacturer-approved positive terminal. The connection must remain protected by the harness fuse. Depending on the engine configuration, the relays may mount on the starboard side near the air silencer or toward the rear of the powerhead using an appropriate coil-plate mounting location. After installation: Secure every terminal and insulate exposed connections. Keep the harness away from the flywheel, throttle linkage, exhaust components, and sharp edges. Reconnect the battery. Test trim-up and trim-down operation. Cycle the engine through its complete trim range while watching for stretching, rubbing, or pinching. Should the switch operate backward, do not randomly change control wiring. Recheck the blue and green motor connections against the supplied diagram. Critical Wire-Stack Positioning CAUTION: The wire stack must be positioned correctly so it cannot be crushed by the clamp bracket as the engine is lowered. Install the wire stack with the product label facing outward toward the installer. Slowly cycle the engine through its full trim-and-tilt range and confirm that the harness remains clear of the clamp bracket at every position. Incorrect routing can damage the insulation, short the circuit, blow the fuse, or cause the trim system to stop operating. Marine Electrical Installation Tips Use only marine-grade terminals, heat-shrink connectors, and corrosion protection suitable for the installation. Do not use household wire connectors or leave butt connectors unsupported. Check the battery, grounds, trim motor, hydraulic pump, fluid level, and mechanical condition before blaming the relays for slow operation. Low voltage, corroded battery cables, poor grounds, a worn motor, or a binding trim assembly can produce similar symptoms. Inspect the fuse holder, relays, connectors, and power terminals regularly—especially on boats used in saltwater. Final Thoughts The API Marine WH476 Trim & Tilt Relay Harness provides a clean method of installing a compatible two-wire API Marine trim motor on select older Mercury, Mariner, and Yamaha three-wire systems. Its two-relay polarity-reversing circuit, color-coded connections, and fused power lead simplify the conversion while retaining conventional blue-for-up and green-for-down operation. Fitment must be based on the original trim-system design and replacement motor number. Confirm the application before ordering, follow the supplied wiring diagram, and carefully check harness clearance through the complete trim range.

Mercury Lake X Observation Tower | History of Mercury Racing’s Secret Florida Test Facility For generations of Mercury enthusiasts, few places have carried the same mystique as Lake X. Isolated, difficult to reach, and surrounded by Florida wilderness, it was the perfect place for Mercury founder Carl Kiekhaefer to test engines, propellers, gearcases, and race boats far from competitors. He simply called the undisclosed location Lake X. Officially known as Lake Conlin, the remote Central Florida lake near St. Cloud became Mercury’s secret warm-weather proving ground in the late 1950s. The roughly 1,400-acre lake offered the privacy Kiekhaefer demanded, and the mysterious name “Lake X” quickly entered Mercury folklore. At the end of the concrete pier stood one of the most recognizable structures in Mercury history: the multi-level Lake X observation and timing tower. With its large round windows, wraparound railings, and distinctive stacked design, it looked almost futuristic. More importantly, it was a working tool. Engineers and observers used it to time laps, monitor test runs, and watch boats being pushed to their limits. Today, that landmark is being refurbished. Recent work on the structure marks an important effort to preserve one of the most recognizable pieces of Mercury performance history. Operation Atlas and the Birth of the Lake X Legend In 1958, Mercury launched Operation Atlas, one of the most ambitious endurance demonstrations ever attempted with an outboard. Two boats powered by 70 HP Mercury Mark 75 inline-six engines ran continuously around the lake, day and night, with the goal of covering roughly 25,000 miles — approximately the circumference of the Earth. The test lasted more than 34 days. Drivers were changed while the boats were underway, fuel was transferred on the fly, and the engines accumulated hours with almost no interruption. Personnel in the observation tower timed every lap and watched the boats as they passed. The leading boat ultimately completed more than 25,000 miles. Combined, the two boats accumulated roughly 50,000 miles of continuous running. Operation Atlas helped cement Mercury’s reputation for durability and turned Lake X into one of the most important proving grounds in marine engineering. From Endurance Testing to Mercury Racing Development Operation Atlas was only the beginning. Over the following decades, Lake X became a critical development center for Mercury Marine, Mercury Hi-Performance, and later Mercury Racing. Engines, propellers, gear ratios, hull setups, drive heights, ignition systems, and complete race-boat packages could be changed, tested, and compared in rapid succession. Fred Kiekhaefer later recalled that the facility kept technicians, tools, propellers, gear ratios, and drive-height hardware ready at all times. He also noted that Mercury’s first V6 outboards, the first MerCruiser sterndrives, and numerous Mercury racing engines were tested at Lake X. From the tower’s round windows, engineers watched the transition from Mercury’s legendary inline-six engines into the V6 era that produced the familiar 2.0L, 2.4L, 2.5L, and 3.0L families. Those engines went on to power everything from fishing boats and bass boats to offshore performance hulls, tunnel boats, drag boats, and purpose-built Formula race boats. The development culture behind engines such as the Bridgeport, Pro Max, 245 Carb, 260 EFI, 280 ROS, S3000, and 300 Drag was built on repeated testing, careful observation, and constant refinement. Lake X was one of the places where that process happened. Some boats left carrying the coveted “Dialed In at Lake X” decal — a quiet badge of serious Mercury performance pedigree. Ownership, Conservation, and Mercury’s Return In 1984, the Lake X property and surrounding land were sold to Kenneth Kirchman, who established the area as a large nature preserve under the Kenneth Kirchman Foundation. The property includes more than 10,000 acres, and the foundation’s mission focuses on conservation, wildlife habitat, longleaf pine restoration, and ecology education. Mercury continued using the core test facility under lease for many years before leaving its original Lake X operation around 2003–2004. The relationship was not permanently severed. Around 2017–2018, Mercury returned under a new long-term lease and again began using Lake X for testing, research and development, boat-builder evaluation, and occasional product and media events. Today the conservation foundation owns the property while Mercury leases the portions needed for marine testing. Lake X remains both a protected natural area and an active engineering site. The Tower’s Refurbishment By the early 2000s the observation tower had already endured decades of Florida heat, humidity, storms, and corrosion. When Scream and Fly documented Mercury’s final days at the original Lake X operation in 2003, the structure was already considered unsafe to climb. Later photographs showed significant deterioration. Rather than allowing the landmark to disappear, recent efforts have focused on refurbishing the tower. The work aims to stabilize and preserve the structure so that one of Mercury’s most recognizable symbols can continue standing on the pier where so much history was made. Modern marine testing no longer depends on an elevated manned tower the way it did in the 1950s through the 1970s. GPS, digital engine management, onboard sensors, remote cameras, drones, and sophisticated data systems now record far more information with greater precision. In its day, however, the tower was an essential instrument. A measured course, a stopwatch, trained observers, and those distinctive round windows were once critical tools of marine engineering. What the Tower Has Seen The Lake X tower watched some of the most important periods in Mercury history. It stood over Operation Atlas and the Mark 75 endurance runs. It was present for the testing of Mercury’s first V6 outboards and the first MerCruiser sterndrives. It witnessed the rise of the 2.0L, 2.4L, 2.5L, and 3.0L racing platforms, countless propeller tests, engine-height changes, gear-ratio experiments, endurance runs, and race-boat setups. For Buckshot Racing #77, that history connects directly to the engines and components we work with today. The classic Mercury V6 two-strokes, EFI systems, race cowls, ignition components, high-performance gearcases, and Mercury Racing hardware that enthusiasts still restore and race were shaped by the relentless development culture Lake X represented. The observation tower is now being refurbished so that piece of history can remain part of the landscape. Lake X itself is still there, still private, and still carrying the influence of decades of Mercury testing. The process that defined the place — run the boat, change something, run it again — helped create some of the most important engines and racing hardware in Mercury history. The tower is being restored. The legend of Lake X continues.

How to Measure Mercury Control Cables | Gen I, Gen II & 33C Throttle and Shift Cables Mercury Gen I, Mercury Gen II & Universal 33C Control Cable Guide Whether you are replacing cables on a classic Mercury Black Max, XR, XRi, Laser EFI or Pro Max, rigging a later mechanically controlled Mercury or Optimax, or building a performance boat with a foot throttle and separate shifter, measure the actual cable-routing path rather than the length of the boat. The same basic measuring method applies to Mercury Gen I, Mercury Gen II and universal 3300/33C control cables, but choosing the correct cable end style is just as important as choosing the correct length. Method 1: Measure the Actual Cable Routing For a new outboard installation, measure from the cable attachment point inside the throttle/shift control along the exact route the cables will follow to the centerline of the outboard engine. Think of the measurement as three sections. Measure from the control box down to the gunwale or rigging tunnel, continue along the actual under-deck or gunwale route to the transom, then measure from the transom routing point to the center of the engine. Follow the path the cable will actually take through bulkheads, rigging tubes and compartments. Do not simply measure straight from the dashboard to the transom. For most outboard installations, add 4 feet to this routing measurement to provide the engine-end loop required for unrestricted steering, trim and tilt movement. The basic formula is: Control to Engine Routing Length + 4 Feet = Control Cable Length Round the final measurement up to the next whole foot. For example, if the actual control-to-engine route measures 13 feet 5 inches, adding four feet produces 17 feet 5 inches. Select an 18-foot control cable. Normally, the throttle and shift cables follow the same route on a single-engine outboard, so that both cables will be ordered in the same length. Why the Extra Four Feet Matters The additional four feet is not simply excess cable. An outboard pivots from port to starboard and also travels through a substantial arc when trimmed or tilted. The throttle and shift cables must accommodate this movement without pulling against the engine linkage or developing a sharp bend at the transom. A smooth engine-side loop allows the cables to move with the motor while maintaining proper throttle and shift adjustment. Sharp bends should be avoided throughout the installation. Dometic specifies approximately a 4-inch minimum bend radius for Xtreme-style cables and approximately 8 inches for many standard 3300/33C and OEM-style cables. Multiple tight bends increase cable effort and can produce throttle friction, difficult shifting and lost motion at the engine. Mercury Gen I Control Cables Mercury Gen I, commonly called the 600A-style Mercury cable, is the traditional Mercury/Mariner control cable configuration used across decades of mechanically controlled Mercury outboards and MerCruiser applications. Dometic identifies the CC179 / CCX179 family as the Mercury Gen I or 600A-series cable. This cable style is commonly encountered on classic Mercury two-strokes including many 2.0L, 2.4L and 2.5L V6 applications such as Black Max, XR2, XR4, XR6, Laser EFI, XRi, Pro Max and numerous Mercury Racing installations using traditional Mercury controls. Engine model alone should not determine cable selection because control boxes and rigging are frequently changed during a boat's life. Verify the fittings at both the control and engine ends before ordering. Mercury Gen II Control Cables Mercury Gen II uses a different cable-end configuration and was developed for Mercury's later mechanical remote-control systems. Dometic identifies CC189 / CCX189 as the Mercury Gen II cable and specifically associates it with Mercury 4000-series Gen II controls. Gen II cables are commonly found on later Mercury and MerCruiser mechanical-control installations, including many applications from the early 2000s forward. A Gen II cable should not be ordered simply because an engine is newer. Mercury used overlapping control configurations, and boats are frequently repowered while retaining earlier controls. Inspect the existing cable ends or locate the part number printed on the cable jacket. Universal 3300/33C Control Cables The 3300/33C universal control cable is one of the marine industry's most widely used throttle and shift cable designs. Standard 33C cables typically use 10-32 threaded terminals at both ends, allowing them to work with a broad range of aftermarket controls, foot throttles, race shifters and engine adapter kits. Universal 33C cables are particularly useful on performance bass boats, tunnel boats, drag boats and offshore boats where the installation may use a Hot Foot-style throttle, separate shifter or custom race control rather than a factory Mercury control box. A 33C cable is not automatically a direct replacement for a Mercury Gen I or Gen II cable. Depending on the control and engine, the installation may require the proper Mercury cable-end adapter or connection kit. Uflex, for example, specifies an adapter kit when its universal 33C-style cable is used in certain Mercury Gen I installations. Method 2: Measure the Existing Cable When replacing cables that already fit correctly, the easiest method is usually to identify the manufacturer and length printed on the existing cable jacket. On many Dometic/SeaStar cables, the final two digits of the part number represent the cable length in feet. A CCX17918, for example, identifies an 18-foot Mercury Gen I Xtreme cable. If the markings are no longer readable, remove the cable, lay it out naturally and measure it from tip to tip. Round up to the next available whole-foot cable length. Do not automatically duplicate an old cable if the previous installation contained tight bends, stretched engine loops or excessive cable coiled under the dashboard. Re-rigging is an opportunity to correct an improper installation. Buckshot Racing #77 High-Performance Rigging Tip After installing the new throttle and shift cables, leave them disconnected from the final engine adjustment until the routing is correct. Turn the outboard completely from port to starboard, then trim and tilt it through its full required range. Watch the cable loop at the motor. Neither cable should become tight, kink, rub heavily against another component or place side-load on the throttle or shift linkage. Once routing is correct, adjust the shift cable first according to the Mercury service procedure, making sure the engine and control are positively in neutral. Then adjust the throttle cable so the throttle linkage returns completely to its idle stop without preloading the linkage. On high-performance Mercury engines, cable adjustment deserves particular attention. An incorrectly adjusted throttle cable may prevent the throttle from reaching full travel or may hold the linkage slightly open at idle. Incorrect shift-cable adjustment can prevent full clutch-dog engagement and accelerate gearcase wear. Choosing Between Gen I, Gen II and 33C Choose a Mercury Gen I / 600A cable when the control and engine use the traditional Mercury Gen I connections. Choose a Mercury Gen II cable when the installation uses Mercury Gen II/4000-series mechanical-control connections. Choose a 3300/33C universal cable when the control system uses standard 10-32 threaded cable ends or when a custom race-control installation uses the appropriate Mercury adapter hardware. The correct cable therefore requires two measurements: cable type and cable length. For an outboard, measure from the control connection through the actual boat routing to the centerline of the engine, add four feet for the engine loop, and round up to the next whole foot. Then verify whether the installation requires Mercury Gen I, Mercury Gen II or universal 33C ends. Measure the routing—not the boat. Identify the cable ends. Add room for engine movement. Measure twice and order once.