99 115 Johnson dies under power

[Grizz747]

I have a 99 johnson 115 OIS 2 stroke. I starts good, idles good. Left the dock and it idled out, hit the lake gave it gas and it jumped up on plane then in about one minute it sputtered and dropped in RPM and kept missing. If I backed off the throttle it would run fine at 2400 PM but no higher. On the way in same thing. I did give it more gas after a while and i jumped up on plane and then the same bog missing. Any Ideas? I changed the plugs, put in Champions and fuel filter. and the same thing happens

 

[tashasdaddy]

Re: 99 115 Johnson dies under power

clogged high speed jets, running hot, shuts motor down to 2400, have you check spark?

 

[khes142]

Re: 99 115 Johnson dies under power

Yes...sounds like SLOW circuit is activating. test temp senders for continuity to the block when motor is cold, and after running for a while.No continuity means no overheat condition. check temp sender wires. On the OIS it is VERY important that the temp sender wires are routed as far as possible AWAY from the spark plug wires.That is per CDI electronics who make a lot of powerpacs for Johnson outboards. That fixed my problem with SLOW circuit activating without a true overheat condition existing. My motor is an 02 90hp with OIS. Naturally you might have a true overheat condition occuring also. I also think I read once that there was a recall for the 115hp OIS to change the temp senders to a slightly higher value(temp)...but I am not positive about that one.good luck

 

[GatorMike]

Re: 99 115 Johnson dies under power

One other thing you might check. I'm not one of the experts but I saw the exact same thing with my 98 115 last summer while on vacation in Marco Island. I drove myself crazy trying to get that thing fixed. Finally I got a wild idea and ran the boat off of an external tank and it ran fine.

Now for the really weird part of the story. In the next condo over from ours a guy was staying who had an identical 99 Wellcraft with a 98 Johnson 115. I noticed he had the hood off his engine all day working on it. I asked him what the problem was and he described the same thing you did, and exactly what I had been experiencing. I hooked my external tank up to his boat and we took it out for a spin and it ran beautiful.

Could just be something as simple as a clogged fuel line or bad squeeze ball. If you have a 6 gallon tank laying around it might be worth a try.