1990 Johnson 25 hp

[crabber1]

Just removed the Cylinder Head Cover and Head and the found no scarring on the cylinder walls. Suspected a Head Gasket problem and found lots of corrosion possibly breaking the gasket seal. Also found carbon build-up on the piston heads and the Head itself. Thermostat is corroded and shot.

Should I leave the piston heads alone?
What should I use to clean the carbon off the head?
Anything else I should do at this point while the head is off?

 

[tashasdaddy]

Re: 1990 Johnson 25 hp

is there any play in the pistons? clean of the best you can. new head gasket, get it running, then do a decarb, to burn that carbon out. this is the procedure i use:
Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

afterwards compression.recheck

 

[crabber1]

Re: 1990 Johnson 25 hp

Very slight play in the pistons.

Sounds like the de-carb process should be done on the water?