J150ELANC - 150 1992 - skipping at idle

[wingoda]

I am a newbie to the forum so if this has already been discussed please don't flame me...

I just purchased a Grady White 19 with a Johnson 150. When we first tried to start the motor there was water mixed in the gas. We put a water separater in-line and flushed out the old gas.

On the test drive of the boat/motor it appears that at idle there is at least one if not more cylinders misfiring. The motor seems strong at full throttle or even half throttle but consistently misfires at idle. At one point the engine suddenly quit. Thankfully it started right back up.

Any thoughts on what to look at first? I have ordered the service manual for the motor but it won't be here for a week or so.

Thanks,
Wingoda

[boats.net]

Sounds like you could have some of the idle circuits clogged with debri, fuel system. Start with checking spark and compression. If both are good, then spray silicone spray through each carburetor (while running and one at a time). If it boggs then that carburetor is fine, if it picks up, then you that is a carburetor that needs repair.