1988 Johnson 88 scored cylinders

[rrw]

Hi, just pulled the right head on my 88, the compression was 120 on both left, 90 on bottom right 115 on top right. Was hoping it was the headgasket, not so lucky. Both cylinders have scoring in exact same spot, about 11 o clock, with bottom being worse, removed a piece of steel imbedded in bottom piston. Looked like rings were intact. Both pistons have a indent in center almost looks like too long of spark plug may have been in at one time. Does that sound possible? Id really like to get one more season from it as is. Should I polish up scoring? It runs ok once warm, worse part is starter keeps kicking out from the bad cylinder. Any advice on making it last till winter? Is there a good chance of it failing all at once? Thanks


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[rrw]

Re: 1988 Johnson 88 scored cylinders

Any advice?

 

[glenn property of pam]

Re: 1988 Johnson 88 scored cylinders

my first test would be to rotate the piston past the tdc then allow it to go about 1/4 down then hold the flywheel and push with the wood end of a hammer on the piston crown gently to see if the piston moves indicating a problem with the bearings allowing the piston to hit the plugs.

"worse part is starter keeps kicking out from the bad cylinder". hmmm what does that mean

the small metal part could be the tip of a spark plug

 

[rrw]

Re: 1988 Johnson 88 scored cylinders

"worse part is starter keeps kicking out from the bad cylinder". hmmm what does that mean, I've read Joe Reeves say that's common on the v4s to have the bendix gear kick out when cranking an engine with mismatched compression.

Thanks for the advice I will test bearings in morning. I've owned this motor over a year, never had any plug issues, but that doesn't mean much considering its 25 years old.

 

[Joe Reeves]

Re: 1988 Johnson 88 scored cylinders

Those indentation on top of the piston are due to the piston rings breaking up.

You have a 30 psi difference in compression between the highest and lowest reading.

Bottom line.... that powerhead requires either rebuilding or replacing. To continue running it will only make matters worse.

 

[emdsapmgr]

Re: 1988 Johnson 88 scored cylinders

Joe has the correct diagnosis. You have two bad pistons which will require replacement, as well as the head. One of the cyl liners looks slightly scuffed. Possible from a lean conditon. Pull the carb apart that feeds the scuffed cyl and see if there are any restrictions in the jets.

 

[rrw]

Re: 1988 Johnson 88 scored cylinders

Ok, that's not what I was hoping to hear. It's been like this since last summer, I'm proly just gonna run it til she blows or til winter then buy a different outboard. I cleaned the carbs over winter, so if that was an issue it shouldn't be anymore. Thanks for the help!