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Mercruiser 4.3 (262) high RPM problem 1989 290

M

mpilot

New member
Hi there,

First post, just found this forum. I have an 89 290 Thundercraft with twin 4.3L (262ci) Merc's in it, and I'm having an issue with the starboard engine.

If I hit full throttle, the motor will go up to around 4300RPM before it starts to choke. It'll then drop RPM and become unstable (stumbles and loses power) until I bring it back down to around 3300RPM, where it hums along just fine. It's responsive and runs great up to that point, but it makes getting off the lake in a storm a bit of a pain :)

Any ideas? I'm leaning toward spark, but also considering fuel delivery.

Thanks,
Chris
 
Re: Mercruiser 4.3 (262) high RPM problem

Make sure all of the plug wires are tight to the plug. Clean the spark arrester. See if there is full free movement on the carb throttles and that the choke throttle is wide open. Spray the throttle shaft ends w/carb cleaner then lube w/a light oil (sewing machine or barber clipper oil works well). When were the fuel filters last changed? One in the pump and one in the carb fuel inlet? Pull the spark plugs and read them; should be tan to medium brown in color. If more towards white then it's too lean. More towards black is too rich. Oil fouled could be worn rings or valve guides/seals. Perform a compression test if the plug colors are out of range.
 
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