15 HP Johnson throttle problems

[superflydudebike]

I am looking at a 1974 Johnson 15 HP motor. It needs a good dose of choking to get it started and then it will run, but never seems to respond to opening up the throttle. The guy said he did not use the motor for a couple of years and then when he went to start it after it sat, he used old gas. He has since used fresh fuel and replaced the plugs, but never gappped them and when I went to look at the plugs, they were so loose that I could take them out by hand. The water is pumping well. It also does not seems to idle well because when it is throttled down, it wants to cut out. When the motor cuts out, it must be choked to restart. I'm thinking it needs a good carb overhaul or are there other issues taking place? Both cylinders seem to be firing and I can get it into forward and reverse without it cutting out. It just never seems to repond to full throttle. Any ideas as to possible problems? It has not had any real service in years.

 

[iwombat]

Re: 15 HP Johnson throttle problems

you're right on with the carb rebuild. I'd be doing the water pump w/o even thinking about it too.

 

[JUSTINTIME]

Re: 15 HP Johnson throttle problems

you're right on with the carb rebuild. I'd be doing the water pump w/o even thinking about it too.

yep i with ya on that one

 

[superflydudebike]

Re: 15 HP Johnson throttle problems

The other thing that I noticed about this motor hen I went to look at it was some oil inside the prop. It was black. It smelled it and it did not smell like gear lube. I'm assuming it was unburnt oil coming out of exhaust. This seems pausible especially since it is having the carb issues. Am I on the right track here? Does this motor seem like it is worth making an offer on? I have not worked on outboards before, but I have done some minor engine work on my car. Will a carb rebuild and a water impeller replacement be that difficult to perform? I'm guessing that the carb rebuild takes more skill than the impeller project, correct?

 

[tashasdaddy]

Re: 15 HP Johnson throttle problems

go to engine faq "awakening a sleeping outboard"

 

[iwombat]

Re: 15 HP Johnson throttle problems

Both jobs are pretty easy. If you've worked on cars before, a manual and a couple of questions here will get you through both w/o any problem.

 

[superflydudebike]

Re: 15 HP Johnson throttle problems

Thanks for the help. Correct gap for these plugs? AC Delco 43.