1992 Johnson 15HP Runs rough mid range

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newbiebassman

Recruit
Joined
Jun 13, 2007
Messages
3
I bought a used 14' boat last season with a 15HP Johnson 1992. It idles & trolls good. Top end is smooth. Anywhere in between runs rough unless there is a heavy load on engine. Boat alone weighs ~400 lbs & rated for 40HP max. Is somewhat underpowered, but I'm usually on fishing lakes with a 10MPH limit anyway. No idea of mechanical history, but previous owner, a nice guy in his 80's, lived on a lake, & fished nearly everyday. (livin' the dream)
Any suggestions? thanks
 
psteurer

psteurer

Petty Officer 1st Class
Joined
Nov 10, 2008
Messages
366
Re: 1992 Johnson 15HP Runs rough mid range

When was the last time the carburetor rebuilt? I am not too familiar with this carburetor but it sounds like there is crude somewhere. Since it idles and trolls well and also runs good at high speed, you could just live with the intermediate speed roughness (unless you always cruise at intermediate speed). You could also try adding 2 oz of Sea Foam per gallon of fuel mix. Sea Foam will not clean your carburetor but you could see some difference by running it. The best fix would be to rebuild the carburetor.
 
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