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1998 40 Johnson speeds up and down without touching throttle

T

tdossey

New member
This motor is a very temperamental thing. But now running great for a while. Start going across lake and the motor will just speedup like you gave it gas but no one has done anything. Then it will just slow down like you pushed the throttle down. But nothing done. This will just go back and forth. Just doesn't make since. ride around the lake at a slow cruising speed just fine. Then head across the lake at just a little faster and the ghost starts driving.

Hope this is explained enough for someone to give me an idea. Thanks
 
Thanks for your reply. I have 2 different tanks. It did it the time before on one tank and this time it was the different tank. haven't tried getting another hose. It will sit and idle forever.
 
Thanks for your reply. I have 2 different tanks. It did it the time before on one tank and this time it was the different tank. haven't tried getting another hose. It will sit and idle forever.
 
I retired in 1991 (OMC Tech) so I'm not familiar with your engine's design or circuitry, however..... I assume that rig has two (2) carburetors and if so, have they been off the engine lately or had the linkages changed, adjusted, whatever?

It sounds like you do not have the linkages between the carburetors synchronized..... one carb set at idle properly, the other set slightly off idle. If so, the engine would run exactly as you describe.
 
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