Johnson 115 SPL engine problems

egscharf

Seaman Apprentice
Joined
Dec 2, 2012
Messages
30
Yesterday, while leaving the harbor, I pushed the throttle forward and my boat got up on plane, only to bog down, then pick up, then bog down, over and over. I found a kinked fuel hose, replaced it, and we were up and running full speed, until I slowed the boat down again. It stalled at idle, and then wouldn't start. I took the fuel pump apart, noticed nothing wrong with it, and put it back together. Same thing. Finally got it started, but only with the engine in neutral with a bit of throttle, I quickly shifted into gear, and was able to limp back into harbor at 2500 RPMs. I flushed the engine with the muffs, but it would only start with a good amount of throttle, and wouldn't stay at a constant RPM.
Sounded like a carb issue to me, so I ran and picked up a rebuild kit, and rebuilt both carbs yesterday.
Still exhibiting the same problem. After trying to start it with the throttle at idle (no luck), I pulled the plugs and noticed that they had lots of black oil sludge on them. Then I noticed that the same black sludge was leaking from my exhaust port. As I was working alone, I was unable to check the spark, however I do have a tester and will check that out next.
Does this seem like a spark issue to you? Engine was recently correctly timed on the water. Also planning to try an isolated fuel source.
Thanks for any help!
Eric
 

egscharf

Seaman Apprentice
Joined
Dec 2, 2012
Messages
30
Re: Johnson 115 SPL engine problems

Also, motor does not have an oil injection system, and I noticed plenty of fuel flowing through carbs when primed.
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: Johnson 115 SPL engine problems

Possible the fuel pump is weak and won't supply enough fuel to run WOT. Next time out, do a test. Take a friend. When trying to run at WOT, have the friend constantly prime the fuel hose bulb. This will force extra fuel into the carb bowls. If it runs ok as long as you constantly prime the fuel hose bulb, you've got a fuel delivery issue-maybe a weak pump. Those engines run somewhat rich at idle, so it's typical to see the plugs look black and wet. Once up on plane, they will turn light tan.
 
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