81 Johnson 15hp Running lean

[bjarnold1]

I recently bought a 1981 Johnson 15hp that runs however only when the choke is partially open. If it's opened all the way the motor dies. I cleaned out the carb and installed a carb kit and it still runs the same. After looking up the part number the carburetor is off a newer 15hp and was wondering if that would cause the motor to run rough?

 

[Rick.]

Re: 81 Johnson 15hp Running lean

I would suggest you clean it again. Use lots of cleaner and follow that with a good amount of compressed air. They don't always come clean on the first attempt. About the carb. being changed I would say it would depend on the year. Best of luck. Rick.

 

[bjarnold1]

Re: 81 Johnson 15hp Running lean

The carburetor is a 1987-1990

 

[bktheking]

Re: 81 Johnson 15hp Running lean

Plastic top carb? If so check it for warpage on the plastic top, it was a problem on the newer carbs, if you want it to run properly put the correct carb on it if in doubt.

 

[bjarnold1]

Re: 81 Johnson 15hp Running lean

It looks like the correct carburetor for it however the float chamber has a part number of 330881 which looks like it's for the late 80's motors. I did a compression check and both cylinders are at 100 when cold and I cleaned all the wiring connections as well

 

[bktheking]

Re: 81 Johnson 15hp Running lean

The float bowl may have been changed but still be the correct carb. Like Rick said, clean it again. 2 things come to mind for idle issues:

1- welch plug at the top, did you remove it to clean the holes in behind?

2- the idle needle screws into a red plastic/rubber seal with an eye on it to keep it from turning, did you replace it?