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-   -   PCM oil usage and low compression in one cylinder (http://www.wakeworld.com/forum/showthread.php?t=793118)

adam4x4 05-01-2012 12:42 PM

PCM oil usage and low compression in one cylinder
 
I have 252 hours on my boat and it has always use bout one quart of oil every 10-15 hours. Shops have told me that is not bad, but I know that my old boat did not ever use any. So this year well they are doing some other stuff to my boat I had them pull the plugs and found one that was black from burning oil. So they did a compression test and found low compression in that one cylinder 160 compared to 190-195 in the others. There telling me that PCM will have them pull out the motor and on that one cylinder hone it, new rings and put it back in. This dose not sound good to me .Is this the way they fix this problem?
Thanks Adam

05-01-2012 12:50 PM

Absolutely yes, thats the only way to do it.

Edit: Ill explain better. The hone trues up the cylinder so that it gets back to being round again. The rings are what gives the piston its compression, so yes this is the way to do it.

Raf1985 05-01-2012 5:24 PM

That sounds about right. A leakdown test will pinpoint exactly where the compression is going. If it is going to the crankcase, then you are looking at rings/hone and possible piston replacement. At that point I would just freshen up all of the cylinders. The major cost is going to be pulling the motor and disassembly anyways, so you might as well get it all done.

bill_airjunky 05-01-2012 5:28 PM

The only other issue it could be is the valves at the top of that cylinder. I believe the leak down test that Raf mentions will determine if it's the rings or the valves.

nitrousbird 05-01-2012 6:50 PM

Unless they are footing the bill and you have no say in the matter, just have them do a full shortblock rebuild. You will have more of a piece of mind knowing the whole motor has been went through. New rings, bearings, and ensure that all cylinders are good to go so this doesn't happen again.


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