85 Johnson 50hp case leak?

[DavidD]

I have a 1985 johnson 50 hp I bought for my mckee craft. The boat it came off of had flipped over during a tornado and port side powerhead mounting bracket had been broken. The engine has 150lbs compression both cylinders. I replaced bracket and cleaned carbs. Engine starts and idles fine. When I raise rpms up around 1200 the engine keeps raising rpms on its own without the carb lever moving. I have to shut off the engine to keep it from getting to high. I'm thinking I might have a case leak letting air in and leaning it out. Any Ideas? Thanks!

 

[boobie]

Re: 85 Johnson 50hp case leak?

Is it doing it on a flusher or in the water ??

 

[DavidD]

Re: 85 Johnson 50hp case leak?

It is doing it on a flusher.

 

[Daviet]

Re: 85 Johnson 50hp case leak?

Run it in a tub with the water level at least 6" above the water pump to put back pressure on the exhaust system. You can also use carb cleaner and spray around all the seals and gaskets and see if you get an increase at idle.

 

[DavidD]

Re: 85 Johnson 50hp case leak?

It appears that the lower carb is spitting gas back out thru the orfice right above the large carb opening. Still scratching my head... Checked the gaskets and powerhead with carb cleaner and didnt find any leaks.

 

[DavidD]

Re: 85 Johnson 50hp case leak?

Installed new needle valve,seat and gasket still spitting gas and when you rev it up acts like it wants to run away. The float is supposed to be level isnt it?

 

[Daviet]

Re: 85 Johnson 50hp case leak?

Yes, the float should be level with the carb body.
Did you get the little roung gasket installed in the carb, #7 below.
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[DavidD]

Re: 85 Johnson 50hp case leak?

Yes installed a new one and also a new bowl gasket. Ive never seen 1 act like this...