occasional sputter

[harleymike]

i hae a 96 mercury force 75hp.
it has an occasional sputter. does it under load. did it today more than normal.
it does a quick sputter than runs fine. then a few min. later does it agian.
it went away after a whiletoday and stopped doing it. it does it at mid too full throttle.
any suggestions.
thanks mike

 

[roscoe]

Re: occasional sputter

Mine will do that if I fill up with cheap gas from the close to home gas station. Or if the gas is real old.

I would start with all fresh fuel.

Suspect water in the gas.

 

[harleymike]

Re: occasional sputter

im going too buy some seafoam and start adding that too the gas also.
i was using lowest octane fuel. i am going too try the 91 (high octane ) fuel and see if that helps also.

 

[roscoe]

Re: occasional sputter

Higher octane does not generally help with a 2 stroke engine, but ethanol free gas is surely a better choice when combatting water in the fuel.

Seafoam will help also.

 

[harleymike]

Re: occasional sputter

just went out again today.
Seemed fine, but then had too tow another stranded boater.
was towing at about 2800 rpms. after about 10 min. started doing the occasional sputterr thing. got worse and worse.
I watched the rpms, they did not move. But the motor would shake when it sputtered.
after i towed him, i ran the boat wide open for awhile, then cruiesed at differant rpms. it ran fine agian. I wonder if its loading up for some reason. It always seems too be around 3000 rpms that it does it.

 

[jason32038]

Re: occasional sputter

Maybe your shift linkage is misadjusted causing to shift in and out of gear rapidly. What kind of noise is it? Can you feel a jolt and a loud noise while it sputters? If so check your linkage.

 

[roscoe]

Re: occasional sputter

If it would shift out and back in, at 3000 rpm, you would know it. The boat would be bucking like a horse. And it wouldn't last long.


Also, from my experience with several of these single carb 70 and 75 hp motors, they tend to have a small dead spot, or flat spot somewhere in the 2500-3000 rpm area. I think it is a quirk of the carb itself.