Engine runs rough with cover on?

J

Jerry Leeman

Recruit
Joined
Mar 15, 2013
Messages
2
I have a 2003 115 4 stroke Johnson. This winter it started acting up by running rough, no top end and hard to start after running for a while. I have changed the plugs, changed the inline fuel filter, added a fuel separator. I have seemed to make progress but I have found that it runs smooth and revs up as long as I have the cover off. I have checked and the cover is not pinching any hose or anything. I made sure there is not air blockage in the vents. It does seem to be an air flow problem. Suggestions?
 
B

boobie

Supreme Mariner
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Nov 5, 2009
Messages
20,826
Re: Engine runs rough with cover on?

I agree with the exhaust leak. Are you running it in barrel or on the lake ??
 
E

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: Engine runs rough with cover on?

A customer complained that the 25 hp engine on his duck boat just would not rev up properly when on the water. He found it would work well with the engine cover off. We found he had put a vinyl camouflauge decal all over the cowlings of the engine, including the air intake vent-successfully choking off the engine. Easy fix.
 
kenmyfam

kenmyfam

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Aug 10, 2006
Messages
14,385
Re: Engine runs rough with cover on?

Any or all of the above statements could well be the issue. Leaning toward the exhaust leak as the most likely cause.
 
coolbri70

coolbri70

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Oct 6, 2011
Messages
1,554
Re: Engine runs rough with cover on?

+1 my bet would be on the exhaust leak
 
J

Jerry Leeman

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Joined
Mar 15, 2013
Messages
2
Re: Engine runs rough with cover on?

It is an exhaust leak. The water jacket gasket is leaking into the cover. Thanks for the comments
 
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