1980 johnson 50hp problems with everything?

[marinus]

I just got a 50hp johnson from 1980. The engine was runnning when I got it but not very good, got soaked after a while and difficult to start again. I cleaned the carbs and replaced the sparks, resulting in better performance but still running like a bad och trash after about 5min.
So my next guess is that I have bad sparks since the engine is running bad on idle and can't rew hard when it's in gear.
The previous owner told me the he had some problems with the overheat alarm so I replaced the impeller and flushed the system, however, the heat sensor in the engine top looks pretty bad, the wire is half visible but I don't get the alarm when I ground it. Could this have anything to do with problem? Please give me some input where to start, my big issue is that the motor is mounted on a boat sitting in the water making it all more difficult to work with.

 

[tashasdaddy]

Re: 1980 johnson 50hp problems with everything?

start by check compression, and spark on both cylinders, you need a spark tester, spark should just 7/16 inch. compression should be 100 psi or higher. but should be with in 5 psi either way. what do you means it got "soaked" not a American description.

 

[marinus]

Re: 1980 johnson 50hp problems with everything?

Ok thanks,
By soaked I mean wet, like it's too much fuel or that it is not burning all of it. Sorry about the wording, I'm Swedish. I will check the compression and spark by tomorrow. Can the overheat switch have anything to do with it? is that somehow connected to the ignition as a killer?

 

[marinus]

missing 150psi....

missing 150psi....

Ok, new info.
I tested the comp and it was 25psi on both cylinders.... Tested to drop some oil in the cylinders and one got up to 75psi while the other stayed at 25psi. Sounds like it might be both pistons and head gasket?
I also tested the ignition with a srobe-light and I could read 4 on idle and 20 on full, using the start motor. But I also noticed before (when it was running( that the idle was very very low. What should be my next step? I can replace the head gasket, but since the boat is in the water, it will be difficult to anything about the pistons since that requires that I'll take the whole thing apart, or?

 

[mars bar]

Re: 1980 johnson 50hp problems with everything?

Hey Marinus is my first name. Named after my grandfather. Not a popular name, but I love it.

 

[tx1961whaler]

Re: 1980 johnson 50hp problems with everything?

Sounds like the head gasket. Take off the cylinder head and inspect the cylinder for scoring. Make sure the cylinder head is flat before reinstalling with a new head gasket. I use a piece of glass with fine sandpaper on it and flatten out the high spots.

 

[marinus]

Re: 1980 johnson 50hp problems with everything?

I'm hoping it's the head gasket, but isn't the increased compression when adding the oil indicate piston rings? Can that be replaced without taking the entire engine apart?

 

[marinus]

Re: 1980 johnson 50hp problems with everything?

Hey Marinus is my first name. Named after my grandfather. Not a popular name, but I love it.

Nice
My name is Linus and I work for the Marine, so i figured Marinus was a good combo.