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Mercury 402 1971 no power under load

Dreux

New member
Hello all,

I recently purchased a 15ft thermoglass with a 1971 mercury 402 40hp on it. The engine seems to run well. idles nicely if a bit fast, shifts gears and throttles up properly while out of the watter on a hose. However when i put it in the water and accelerate the engine does not obtain proper rpm or speed... I have cleaned and redone the carb, the filter looks fine. Any input or thoughts would be much appreciated.

Thanks in advance. 😁
 
They run surprizingly well on one cylinder !!----So do a compression test.-----Then check for spark on both leads.
 
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