compression problem

[ft1]

i got a 1979 235 evinrude 1 cylinder has 60 pound and holding the compression all others have 110 i took the heads off and the walls look great i tried to move the piston to see if it was loose and it's not boat was standing for 2 years any suggestion

 

[Joe Reeves]

Re: compression problem

If the engine was runable, it would have been best to run it for 10 or 15 minutes, then to check the compression. You don't say one way or the other.

However, if you checked the compression more than once and are sure that those are the correct compression readings, the engine is due for a complete teardown in order to repair/rebuild properly.

 

[boobie]

Re: compression problem

Whats the head gasket look like ?? Stuck rings ??

 

[ft1]

Re: compression problem

the head gasket where in very bad condition

 

[ft1]

Re: compression problem

the engine is runs i ran it for more than 15 minutes yesterday and then today i check the compression but i see no damage to the cylinder wall even look better than the one underneathe which has 110 compression

 

[boobie]

Re: compression problem

Did you replace the head gaskets. If you did, what's the compression now ??

 

[ft1]

Re: compression problem

Did you replace the head gaskets. If you did, what's the compression now ??

i will today will let you know

 

[ft1]

Re: compression problem

i just replaced the head gasket and put seafoam still 60 lbs compression no play on piston no scared cylinder wall took out side panel and looked at piston and ring they look great can it be stuck ring since it was sitting for 2 year it runs good if it's stuck ring how do i unstuck them

i will today will let you know

 

[boobie]

Re: compression problem

How did you use the seafoam ??

 

[Joe Reeves]

Re: compression problem

Of course, since you've already replaced the head gasket, use the seafoam as per Boobie's procedure/instructions.

I assume that you did closely inspect the sealing areas of the cylinder head and crankcase/block?

 

[emdsapmgr]

Re: compression problem

You may want to get a closer look at the ringset on that low compression piston. Suggest you remove the side cover on the block for that cylinder. (called a bypass cover.) Once removed, you can view the piston rings and piston skirts for carbon buildup. Slowly rotate the flywheel by hand to see if the rings appear to move freely in their groves. Not a difficult thing to do, but you will need a new cover gasket (307133-about $2- when you reinstall it.) Original factory pistons in that year were unusual. The top ring groove is cut right at the top of the piston. While that yielded max compression, it was a long-term potential failure (weak) point. After a year or two, OMC re-designed the pistons and moved the rings slightly lower on the piston. While NLA, racers still seek out these old pistons for their performance potential.