20 HP 1980

[shrimp92]

I have a Mercury 20 Hp 1980 model. I just got the carb readjusted. But I've taken out about 3 times. But yesterday, it started making a noise like hard knock back and forth at full throttle. Runs ok. Top end seems little different. Is this anything serious or just an old motor.

 

[Yepblaze]

Re: 20 HP 1980

I've heard it mentioned that some of those motors (unsure on years), would have problems with the upper crankshaft bearing.<br /><br />Especially if the little tube hose from the bottom bearing to the top was leaking or otherwise not working.