6hp Johnson, runs good only with cowling off

[custer]

Motor (in tank) idles forever, runs forever in gear at low speeds. As soon as I open throttle to WOT it does fine for 10-60 seconds then starts bogging.

I take the cowling off and there are no problems....

What up with this????

 

[artherm]

Re: 6hp Johnson, runs good only with cowling off

I am no expert on this, but I can tell you of a problem with an older 9.9hp Evinrude that I was rehabbing for my son. It had the same problem, that I just couldn't figure out. I went to my trusty OMC mechanic for advice. He told me of a seal in the lower unit that was probably leaking exhaust back into the cowling. With this old engine, he said it wasn't practical to rebuild. He made several suggestions including venting the cowling, which I did. I cut two 3" holes in the back of the cowling with a hole saw, and then used Bondo on the inside with large expanded wire. It finished off real nice. I repainted the cowling, and added new decals made from a detail shop. The motor now runs fine.

 

[Daviet]

Re: 6hp Johnson, runs good only with cowling off

It sounds like you might have a leaking powerhead gasket, not really a hard fix on your engine.
With the engine running in a tank with the cowl off, squit some oil in the carb and look for smoke coming out between the powerhead and the exhaust housing.

 

[tx1961whaler]

Re: 6hp Johnson, runs good only with cowling off

Some engines only do this in the tank because it is breathing its own exhaust. It may not do it on the boat in the water.
Or you could have an exhaust leak.
You can check by running a fan outside to blow away the exhaust smoke when it is in the tank.

 

[custer]

Re: 6hp Johnson, runs good only with cowling off

It sounds like you might have a leaking powerhead gasket, not really a hard fix on your engine.
With the engine running in a tank with the cowl off, squit some oil in the carb and look for smoke coming out between the powerhead and the exhaust housing.

Do you mean the "exhaust" cover on the side of the power head???

 

[F_R]

Re: 6hp Johnson, runs good only with cowling off

Hey, custer, there probably isn't anything wrong with your motor!!! Running in a tank with the hood on will cause it to bog because it is breathing its own exhaust. Stick your nose down in there near the bottom of the hood and you will see what I mean. You won't be able to breathe any better than the motor does. Get it out of that tank and on a boat on the lake and you probably will find that it is fine.