1996 Johnson 50, J50TLEDS, Pulled head, Need opinion on codition of Pistons/Cylinders

[paul_yegr]

I tested compression. I got 15psi out of the top and 40 out of the bottom. To test compression all I did was pull the plug and stick the tester on and crank it. Now I read, I maybe should have had the opposite plug out... Anyways, pulled the head and here are the pictures of the cylinders and pistons.

1. Does anyone with experience know whether a bad head gasket could cause this much low compression?
2. Is the scarring on the cylinder wall past the point of being operational again?
3. You can see there is a little larger gap in between the top of piston 1 and the cylinder than there is on the bottom of that same piston.
4. Is there a point in changing the head gasket and buttoning it all back up to see if I can get some better compression?

Thank you very much!!

 

[racerone]

If there is scoring on the cylinder wall then there is no option but to tear it down for rebuiding.-----Either you compression tester is way off or your motor is in bad shape !!!

 

[MikDee]

I see 5 little x-boxes no pix???

 

[paul_yegr]

I don't know if scoreing is the right term. Can you see it in the pictures? It's like rippled, not horribly but you can feel it and you can see it in the pictures, just that upper cylinder.

 

[racerone]

If you can feel it with your finger nails then the motor must come apart !

 

[rothfm]

Cant see pics....I have issue with pics after the site update. Nothing I do, including photobucket works. Sorry to reply here. But Frustrated with pics also.

 

[AlTn]

one other tidbit in your decision...roll each piston past tdc so it's an 1/2" or so down in the cylinder then, hold the crankshaft steady with the flywheel or some other means, and push on the piston top with something that won't scratch it < wood dowel, plastic screwdriver handle, etc.>..do you hear/feel a click or see some movement in the piston?..if so, you probably have some bearing wear in the wrist pin or connecting rod bearings. You can determine how much you want to tie up in this motor if a rebuild is deemed necessary.

 

[racerone]

Scored pistons are fairly common in these motors.---See it all the time.---Motor must be torn apart for boring / honing of at least the top cylinder.