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Compression of 92 Yamaha 250 OX66, 250 hrs after rebuild.

I have the opportunity to purchase one of 2 1992 250 OX66 saltwater series engines. They were rebuilt 250 hrs ago and has 105 psi compression. It is the starboard or right hand motor on a 31' Fountain. The port motor already sold and had 113 psi. Is it possible that this starboard engine was propped wrong and was carring the bulk of the load? Assuming that and that I will only lightly use how say 75 hours per year how many years can I go till another rebuild?

Posted by Anonymous on

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  • Boating Master
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Hey Anon,
The biggie is the compression difference between ALL the cylinders,,, there should not be a 5-10% max. difference between the lowest and highest readings.. if more.. I would question the rebuild quality,,(My V6 is all within 5 psi after 13 years - (I rebuilt it!!) The longevity is based on how hard you run it, the quality of the oil and fuel you run and how clean you keep inside the cowl....
The engine could last for a long time.. or break tomorrow...no way to know??

Posted on Jun 21, 2017

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Posted on Jan 02, 2017

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SOURCE: Compression of 92 Yamaha 250 OX66, 250 hrs after rebuild.

you could get 20 + years out of it with proper service

Posted on Apr 25, 2010

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