1988 Johnson 15 won’t stay running….

J

Jordankato

Recruit
Joined
Apr 3, 2026
Messages
5
So I just came across a 1988 15 hp Johnson outboard and I know it started and ran before I got it. I put a whole new fuel pump on it. Brand new carburetor on it and redid the wires. It’ll start up from the battery and the push start, but it will not stay running it revs up really high. I can almost use my carb idle adjustment and get it to lower, but then it gets too low and just dies any help would be awesome or insight of the matter.
 
R

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
39,494
I always ask folks to post the actual compression values,----Need to establish condition of the engine,-----Where did you purchase the pump and carburetor?----I would have repaired the pump and carburetor you had, very easy to do.
 
J

Jordankato

Recruit
Joined
Apr 3, 2026
Messages
5
The carburetor got ruined. In the brass plate, a screw stripped out and couldn’t be easy outed. As for the fuel pump, I probably should’ve rebuilt it. I just bought a new one, but I also have seals coming for the old one just to have an extra. compression is good in 120 and 110 in each. I bought parts off marine engine and Crowley. The carburetor was off eBay. It was remanufactured.
 
J

jitterbug127

Senior Chief Petty Officer
Joined
Feb 6, 2023
Messages
673
I ran into this last summer on a 15 i had. I'd start with checking your low speed needle on the carb. It needs to be around 1.5 turns out. The other thing you can adjust is the low speed knob on the actual throttle handle. In Neutral You should be able to move it a bout 1/8 of a turn to start and then can turn it back to idle down. Put a tach on the motor. Idling around 900 rpm is ideal. Its hard to dial in without an cheap tach. 10 bucks amazon.
 
J

Jordankato

Recruit
Joined
Apr 3, 2026
Messages
5
So after work today, I got home. It was the roller knob on the carb. It was screwed in too much, unscrewed that started right up stayed started
and then I just had to adjust with the low idle needle.
 
S

saltchuckmatt

Captain
Joined
Jul 19, 2019
Messages
3,179
Lots of terms I've never heard of. To answer racer question, were the parts ordered OEM?

Also, there was a 10 lb difference in the compression reading?

Just because it starts and runs now doesn't mean it will push you down the lake. Under load will be the next test.
 
J

Jordankato

Recruit
Joined
Apr 3, 2026
Messages
5
saltchuckmatt said:
Lots of terms I've never heard of. To answer racer question, were the parts ordered OEM?

Also, there was a 10 lb difference in the compression reading?

Just because it starts and runs now doesn't mean it will push you down the lake. Under load will be the next test.
Click to expand...
I’m curious as to the terms you’ve never heard of because I’m using the terms that come straight off the diagrams.
 
You must log in or register to reply here.
Top