Compression Varation and self mixing oil

[che]

Gday,
I know this has been discussed a few times, I have 1990 model outboard 150 Merc, its compression is all around 110, then 6th: 125, (claimes the repair man) when i got the boat checked three months ago it was said to have 99, 110,110,110,110,116. is this likey compression testing differences?

ofcourse he wants to rebuild it (3,000 dollars). I have a feeling that this baby could go another few years without a rebuild, then if it does, im in no worse a position....or could it cause some serious damage?

Also what do people think about changing to pre mix (manually), rather than having a self mixer for the oil?

thanks In advance.

 

[Plainsman]

Re: Compression Varation and self mixing oil

Gday che and Welcome to iboats!

Even though the 125 is higher, it still falls within the 10-15% range. Maybe a good decarb (see the FAQ's on how to do this) will help even it out more.

Can you take to someone else or maybe check the compression yourself to verify the numbers?

 

[emckelvy]

Re: Compression Varation and self mixing oil

A friend of mine was looking at an older V6 Merc with even compression readings except for one cylinder that was unusually higher, similar to this one.

Turns out that the sleeve in that cylinder had shifted, which apparently caused the strange reading. Never heard of that one!

At any rate, I'd do the de-carb as suggested; take my own compression readings with a quality gage; then, if things are still 'strange', pull the cyl head on the 'suspicious' side and inspect the cylinder carefully.

The cost of a head gasket is slight compared to the $$ saved by catching a potential problem early and possibly nipping it in the Bud before it perhaps renders the block non-repairable.

HTH............ed

 

[che]

Re: Compression Varation and self mixing oil

Thanks a lot guys,

will do