15hp Johnson Issue, fuel related?

[kidafa]

Hi all,


So this season I have purchased a tinny with a 15hp Johnson O/B on it..... Used it about 5 or 6 times mixing it 30:1 and its been running fine until recently its got a weird hickup.

Ill be driving along and then it will die right off and not go very fast at all even on full throttle. Turn it off restart same problem, play with throttle position and still it doesnt rev any harder. Some times if I hold it flat after a while it splutters a bit and then runs hard again other times it doesnt.

The issue has been intermittent one trip I didnt get it at all but last trip Its all I got and nothing else.

Last trip I pulled the plugs out in the water and ONE WAS DRY. So im guessing its a fuel issue? Blocked jet maybe? Can some one give me some info on carby cleaning/rebuild for this beast?

not sure on the year as we tried to discover it earlier check here : http://forums.iboats.com/showthread.php?t=447942

 

[henfjel]

Re: 15hp Johnson Issue, fuel related?

30:1?? sounds like alot of oil. doesen't almost all evinrude and johnson outboards use 50:1 or 100:2?

 

[OptsyEagle]

Re: 15hp Johnson Issue, fuel related?

It might also be a spark issue causing one cylinder to fail. They run pretty good on one cylinder but don't give out the total power under load. The first quick check is to put in a new set of spark plugs and if that fixes the problem, then you know a plug was fouling. If that is the case, you will need to figure out why it is fouling and fix that. I would go to 50:1 oil right away, anyways.

The next test if it passes the new plug test (by passing I mean you still have your problem and hence it was not a fouled plug) is to get a spark tester and check to see if it can jump a 7/16" gap.

If those tests work OK and your spark is fine, then I would look into fuel delivery issues. The most common being a dirty carb.

 

[James R]

Re: 15hp Johnson Issue, fuel related?

30:1 is way too much. No wonder it is strangling. For successful operation do as you have been told so far and get to cleaning and rebuilding the carb real soon.
Another important aspect for your motors health is the water pump impeller. If you don't know when it was last replaced replace it.

 

[kenmyfam]

Re: 15hp Johnson Issue, fuel related?

What year is the motor ????
Basic health check to begin with.
Compression
Spark
Fuel delivery
Spark plug condition.
Post results.