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40 HP Merc idle revs up and down.

J

JP102

New member
1980 2 cyl 40 hp merc. I just rebuilt the carb and replaced the fuel pump now the engine revs up and down at idle. Start at 800 rpm , revs to 1600 rpm and then down to 800 rpm, keeps doing this. Any ideas on where to start?

Thanks in advance to all.
 
sounds like there is not enuff fuel in the carburetor.-----------------When you operate the bulb on the hose ( a manual fuel pump ) does the rpm change the same way ???
 
Did not think to try that at idle. I did notice that the fuel filter canister was 3/4 full. I will try pumping the bulb. If pumping the bulb changes the behavior, would you guess that the issue is before or after the fuel pump?
 
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