1981 Mercury 80HP 4-Cyl 2-Stroke Compression Range

RuthlessINXS

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Jul 5, 2012
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Is there anyone by chance that happens to know what the acceptable range on a compression test a 1981 Mercury 80hp, 4-Cyl, 2-stroke is? I just got this engine w/ a boat and am trying to make sure the engine is up to par and tuning. Thanks in advance to anyone who can help.
 

Texasmark

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Dec 20, 2005
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Re: 1981 Mercury 80HP 4-Cyl 2-Stroke Compression Range

I have a 2 stroke engine and the operators manual says 120 or more ok, less be skeptical. Thing desired is 10-15% commonality in cylinder to cylinder readings, but you still need a minimum threshold.

Mark
 

RuthlessINXS

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Jul 5, 2012
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Re: 1981 Mercury 80HP 4-Cyl 2-Stroke Compression Range

I was able to get the compression tester on the top 3 cylinders and they all read @ 120PSI almost exactly. I couldn't get to the fourth one due to the length of the adapter and the cowling being in the way. I'll work on getting a different tester and see what I'm reading on the 4th cylinder but I am hopeful. Thank you for the info.
 
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