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Engine Swap - Things to think about before starting a 3 cylinder swap

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Expectations:

  More Speed - reality is same top speed

  More Power - a little more torque than 60hp wetbike

• Mods - same as 60 but 1/3 more work

  Handling - will feel a little heavier than a 60 - especially in the corners

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Planning - What does the project entail?

  Engine Choices - differences through the years

• Casting differences
• Exhaust/bottom of motor is different (early years vs later years) 
• Requires welding up of 1/2 of the exhaust outlet
• Requires welding up of the motorplate to match water jacket routing and gasket sealing surfaces - see here
• Oil Injection Systems - remove the pump shaft and make a block-off plate
•  Ignition Systems - flywheel and stator assys are different
• Early systems had symmetrical bolt pattern (4 bolts)
• Later systems had one hole that was moved outward (flyer) and different flywheel
• All electronic systems (no manual advance) had advanced stator setup and different flywheel
• Pump Shaft Issue
• Option 1 - rebuild 3 cylinder crankshaft and put 60hp lower wheel on (and run appropriate sized seals)
• Option 2 - make a pumpshaft for a stock 3 cylinder motor
• uses a stock propshaft, cut to length, and machine splines on one end
• illustrated here
• Throttle Issues
• wetbikes use motorcycle-style pull-only hookup - outboards use a push/pull morse cable setup
• ignition advance on early motors is controlled by a spring-controlled linkage - makes for a "GORILLA THROTTLE" - see here
• Clearance Issues
• Seat Height - interference with nylon seat bases?
• Throttle - Idle position indicator
• Coils - need to be relocated to right-side of motor (requires lengthening wires) - see here
• Electronics Issues
• Waterproof all connections required
• Waterproof CDI and controller box on newer motors 

• Throttle Hookup Issues
• Mikuni SBN or BN's will require mechanical linkage between the carbs and a standard wheel on one of the carbs
• stock outboard carbs can be used - AND - you can use a stock wetbike/seaflash style hookup
• requires you to grind off the "mashed" end of the throttle shaft and drill/tap it for a tiny screw - see here and here
• Then you use a stock throttle cable bracket on the top carburetor
• Won't work on newer motors that have the throttle-position sensor on the middle carb (not enough room) - see here