mercury compression specifications

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skenniston

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Nov 11, 2009
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I am looking at buying a merc outboard - 1997 250 hp EFI with an hour meter showing 178 hours. Compression check shows 100,105,100,110,105,100. What should this motor have for compression with these low hours, or am I being scammed and the motor really has 500 or more hours???

Thanks
 
Bifflefan

Bifflefan

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May 27, 2009
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2,933
Re: mercury compression specifications

My 74 Johnny has compression at 120 with who knows how many hours on it.
But that is all i can offer you...
 
daveswaves

daveswaves

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Mar 22, 2002
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Re: mercury compression specifications

skenniston said:
I am looking at buying a merc outboard - 1997 250 hp EFI with an hour meter showing 178 hours. Compression check shows 100,105,100,110,105,100. What should this motor have for compression with these low hours, or am I being scammed and the motor really has 500 or more hours???

Thanks
Click to expand...
Bearing in mind there are a lot of things that can affect compression testing, not the least of which is highly inaccurate pressure gauges, test being run without the throttle open, dry cyl, carbon build up.....those numbers look low. I would expect a 3 litre 250 hp in good condition to read about 20 pounds higher. The good news is they are relatively even numbers. I would not discount the engine based on those numbers alone. The general condition of the motor should indicate low or high hours as well. A merc dealer can connect to the ecu and tell you more. It may be worth it.
 
JB

JB

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Re: mercury compression specifications

The engine is fine. There is no spec, mostly because of the things Daveswaves mentions, but also because no known fault would cause 6 cylinders to all go bad by the same amount at the same time.
 
daveswaves

daveswaves

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Mar 22, 2002
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Re: mercury compression specifications

JB said:
The engine is fine. There is no spec, mostly because of the things Daveswaves mentions, but also because no known fault would cause 6 cylinders to all go bad by the same amount at the same time.
Click to expand...
Thanks JB, succinctly said.
 
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