7.5 johnson

[dukekas]

Engine has an low low idle buck or a lean sneeze. Changed plugs, Good spark, swapped tanks, good gas, good fuel bulb, Runs in 2 cycle high rpm. No help with low Idle fuel mixture screw in or out other than smokes pretty good win rich. Fuel pump is pushing but no psi test. Engine wont start unless 3/4 throttle. Ran like a top before problem, acted like it dropped a piston. There was no smoke in gear or very little, good smoke at idle. early 80's Sea Horse model engine. My buddy;s boat he let me borrow, prb happened with me in it HELP

 

[Daviet]

Re: 7.5 johnson

Need more input.
What is your model number? Have you checked compression?
Did you check spark with a tester or by holding a plug next to the block?
Does it run any better if keep pumping the primer bulb?

 

[dukekas]

Re: 7.5 johnson

Looks like a 1982, MD # J8RCNR
Held plug next to block, pumping fuel bulb dosent help, No Compression test. The prb was all the sudden, not a slowly get worse one.

 

[Daviet]

Re: 7.5 johnson

Holding the plug next to the block will not give accurate results, spark should jump 7/16" and be bright blue.
The compression should be one of the first things to check when troubleshooting an engine. You can blow a head gasket or break a ring in a few seconds. Just because it happened suddenly does not mean it might not be a compression problem, check it and eleminate that part of the test.
If adjusting the low speed needle in and out has no effect on the engine, you may have a carb problem.

 

[dukekas]

Re: 7.5 johnson

There is an allfull lot of oil in the water, plugs will def get wet on a richer setting. Your right. Maybe I can rent a compression checker from Advanced. They have a great loaner thing. Whats the threshold for that motor on compression? Spark will jump and feels pretty strong it will jump 7/16 easy, I can attest. Motor had new points and condensers less that 3 years ago, OEM parts Im told. Thank you for helping.

 

[Daviet]

Re: 7.5 johnson

Hold on a minute, that model number does not have points and condensers.
It should have 2 coils mounted on the cylinder head, 1 for each cylinder.
Are we both talking about the same engine?

 

[dukekas]

Re: 7.5 johnson

Yup it does 2 coils . It has a elec spark control, I was thinking of a 9.5 when I said that.