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Mercury 150 4 Stroke running rough

R

RINGRAM

New member
Hello All,

I have a Mercury 150 4 stroke outboard. The motor runs fine for about an hour, then starts running rough. However, it will run fine when at idle speed. No idea on what it could be. Any help would be greatly appreciated.
 
RINGRAM said:
Hello All,

I have a Mercury 150 4 stroke outboard. The motor runs fine for about an hour, then starts running rough. However, it will run fine when at idle speed. No idea on what it could be. Any help would be greatly appreciated.
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I failed to mention the tell tale seems to be putting out water just fine.
 
Describe more of running rough, Is your engine surging in RPMs, does it seem like its missing at what rpm does it run poorly. Have you checked the boat fuel water Seperator as a full separator will allow clean gas to pass thur but if you rev the engine it can get suck up some water into the engine. Also the inline fuel filter on the side of the engine seems to be easily clogged causing surging or limited rpm issues. Other issues Ive seen with Mercury fourstroke 150 is idle air control valve. Easy swap out not to expensive. It caused engine to run poorly at idle and after the initial start it wouldnt restart or you had to advance the throttle to get it to restart. they had a recall on 50-115hp IAC valves but 150 uses same part number
 
Well, i will be running down the river and after about an hour the motor will start shaking. just had the boat serviced. I'm thinking it is either the popper valve or the thermostats.
 
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