We have a 1992 Yamaha WaveRunner III that has recently developed an anoying problem. It starts fine when cold or hot, but after operating for about three minutes the engine RPM is limited to about half throttle or less. If you throttle it more then about half throttle the engine dies. We have replaced the fuel filter, installed new plugs, and replaced the cdi unit with a MSD enhancer unit under assumption that the overtemp circuity had failed in the stock unit. The MSD unit didnt correct the problem. We also ran the CDI with the thermoswitch electronically disconnected with the same results. To add to the confusion the engine does not show any other signs of overheating, such as being hot to the touch or crackling noise from thermal expansion. If the engine is turned of and restarted after it goes into this RPM limit phase, The engine seems to run at full rpm for another few minutes. seems like the problem is in the rev limiter. what do you think?
T.B. I would recommend looking into a fuel system as possible problem. Check the carburetor diaphragm and make sure it has not dried out or stiff. Also there is a small filter in carb that you should check to make sure it is not clogged. Also check your reeds to make sure they are not worn out. The fuel system should pressurize so make sure your gas cap seal is in place and the gas cap does not have any cracks. When open the gas cap you should he pressure release. Good Luck
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