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Question

I have a 1994 mercruiser inboard fresh water cooled engine that runs very rough at idle. the rpm's seem to fluctuate between 400 and 700. It runs great at anything over a 1000 rpm. I have done a complete tune up and have also replaced the carberators.   Any suggestions where to look next?

Submitted: 183 days and 2 hours ago.
Category: Boat
Value: $15
Status: CLOSED

Accepted Answer

Hello,

I would start with a cylinder compression test. They should be no lees than 100 psi and within 15 lbs of each other. If the spark plugs are black then you are getting to much fuel at idle.

 

The idle mix screws (2) are at the base of the carb. Turn them clockwise until the engine runs slower and then turn counter clockwise until the engine runs smooth. Do this with each screw

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Expert: Mechman45
Pos. Feedback: 97.2 %
Accepts: 
Answered: 5/25/2009

Marine Mechanic

30 Year Service Tech Gas/Diesel.

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