Compression Spec on 1993 Evinrude 150HP

plsports

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Aug 27, 2009
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title says it... going to look at a boat with spark issues and was going to check compression it. spark doesnt bother me as long as compression is good. im just wondering what this engine should be running for compression.
 

wilde1j

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Apr 15, 2002
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5,964
Re: Compression Spec on 1993 Evinrude 150HP

Over 100 psig and within 10% of each other.
 

JB

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Mar 25, 2001
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Re: Compression Spec on 1993 Evinrude 150HP

No. The big V6s often measure in the 80-90psi range. The 10% still holds.
 

wilde1j

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5,964
Re: Compression Spec on 1993 Evinrude 150HP

JB, you are quite right. I just wasn't paying attention! The V6's often read quite low indeed.
 

JB

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45,907
Re: Compression Spec on 1993 Evinrude 150HP

Just got a PM questioning if big V6s "should" read 80-90psi.

There is no "should". There are too many variables. One engine, measured by three different people with different guages and under different conditions will give readings varying by as much as 20-30psi.

The only real value of compression testing multi-cylinder 2 stroke outboards is to identify single cylinder or adjacent pair failures. All 3, or 4, or 6 cylinders simply do not go bad by the same amount at the same time.
 
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