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84 Johnson 115 oceanrunner, bogs down near 3000 rpms

E

emac

Regular Contributor
Hi, just got this boat-motor. Engine ran great on sea trial two weeks ago. Full throttle no problem, sounded great. Brought boat to slip, it sat for a week, I took it out today, starts no problem, strong pee stream. once i hit the no wake zone, slowly opened it up. at about 2800 rpms, it started running really rough, got no increase in power, and engine smoked more. Its a 2 stroke so theres gonna be some smoke, but this was more than I expected. again it ran great on the sea trial, full throttle, no bogging or shaking.
Cause its on a slip I did tilt engine up so it wasnt sitting in the salt. I remember with my old mercruiser it was best to pull the gas line and let it run dry. could this be carb issue?
 
not much about history, previous owner said it was maintained professionally, it ran great two weeks ago, will check plugs, I know its the obvious, and fuel filter, I should mention that the engine also does the same in gear or not in gear. Picked up two boats at once, but I expected this one to run... still a month and a half of fishing left, don't wanna miss it.
 
Aw geez....If only we could get real info on here.

OK.....It is probably hitting SLOW mode (SINCE IT IS A 98 AND NOT an 84).

SLOW due to overheat. Check into it. 2500 is the magic number on when to suspect SLOW on outboards so equipped.
 
OK, will look into that. Pee stream is strong, sorry, I'm working on two engines, and confused the engine and boat years...
 
Ok...I see.

Use digital IR temp gun to read actual temp of head when "bogging".
If not hot, suspect the sensor itself.

Disconnect the tan wires at sensor temporarily to isolate problem. If disconnected wire corrects issue, suspect bad sensor.
 
couldnt get problem to replicate. odd. I love when engines fix themselves, maybe there was some sort of blockage on the intake. Pulled cover off and placed hand on flywheel, and it wasnt hot after running for 1/2 hour opened up.
 
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