Johnson 15hp surging, bogging down, low power

[Conway Cox]

I have a Johnson 15hp 1988. I bought it rebuilt a year ago. It has worked great untill now. It starts and idles fine. even goes into gear and runs fine at idle speed. When I give it gas it starts to go but then loses rpm. Does'nt really stall out but slows down in rpm. It will not reach full throttle. Seems to do the same at any speed. Runs fine at low speed but anything more and it seems to not reach full speed and will run at a lower speed roughly. Sometimes stalls when running at high speed and then throttle down to idle speed. I've replaced the fuel pump and did not help. Next step is cleaning carb but don't think is the problem since carb was rebuilt a year ago.Dirty carb? Compression? Spark plugs? Points? Coils? Please Help!

 

[tashasdaddy]

Re: Johnson 15hp surging, bogging down, low power

replace all fuel lines with B1 rated alcohol resistant fuel lines, also clean the carb, particularly the high speed jet, and the center pick up tube. use a rebuild kit. flush fuel line before connecting to the carb.

 

[mikesea]

Re: Johnson 15hp surging, bogging down, low power

Yep,typical dirty carb problem,cant leave those engines with old fuel for long

 

[outboardnut]

Re: Johnson 15hp surging, bogging down, low power

check your fuel filter screen

It's on the side of the motor...fuel pump cap...should be able to loosen with a coin.

Give the fuel bulb a pump while you have that off and make sure you don't have a tank restriction.

Sometimes when fuel pumps go out they will cause surging on the high end. When running the motor "help" the fuel pump a a little by applying light pressure on the primer bulb. If it clears up think about a new fuel pump.

If not it sounds like it's time to rebuild or clean the carb.