Cover on - won't run

[boatbum]

I replaced the plugs on a friend's 1972 25 hp Johnson because it ran rough with the old plugs. It started and ran much better. But when I put the engine cover back on, the idle began to get slower and eventually died. I removed the cover and the engine started right up. I put the cover on again - same thing. I removed the cover when the idle started getting rough, and it smoothed out again. All I did was change the plugs. Even though it ran rough with the old plugs, it ran with the cover on. I don't get it. Any ideas?

 

[ezeke]

Re: Cover on - won't run

Sounds like you are getting exhaust leak.

 

[rickdb1boat]

Re: Cover on - won't run

Check the cover carefully and see if anything may be hitting when it goes on(Like carb linkage) or obstructing the carb opening. Also, put the hood on very slowly and see if it only starts to run bad toward the last bit. If so, it probably is an exhaust leak as was mentioned.

 

[roscoe]

Re: Cover on - won't run

I recently bought a motor, real cheap, which was doing the same thing. I messed with it for a while, then decided to make a low offer, he accepted. I didn't tell him about the 2 wires I found, that were obviously getting pinched (insulation wore thru) when the cover was put on.<br /><br />Runs pretty well now after repairing wires.<br /><br />Exhaust leaking back into engine area will suffocate the engine.

 

[boatbum]

Re: Cover on - won't run

Thank you for the quick responses. I'll try all of your suggestions and see what happens.

 

[ED21]

Re: Cover on - won't run

You might also check the air intake in the cover. It could be blocked w/ wasp nest, foam or rag.

 

[ob]

Re: Cover on - won't run

Look closely in the area of the engine cover latch as well to insure that the bottom plug lead is not going to ground on it when cover is installed.