what should the compression be in a well functioning motor?

[bluebrownie]

i checked all 3 cyl. and had about 130 in each.... i know the differential between cylindars is important, but what should the optimal numbers be? how high should they be?

 

[freddyray21]

Re: what should the compression be in a well functioning motor?

130 is good. I have have some at 140 but 130 is excellent as long as they are in 10%.

 

[jay_merrill]

Re: what should the compression be in a well functioning motor?

Depends on the motor. By saying that you "checked all three," I will assume that you have an OMC, three cylinder looper - 60, 65, 70 or 75 horsepower. Compression values of 130 in all three are good, both in terms of the level of compression and the balance between the three. Absent any other problems that you might know about, it sounds like you have a healthy powerhead.

 

[kenmyfam]

Re: what should the compression be in a well functioning motor?

Compression testers vary in their accuracy. Over 100 and within 10% as stated and you are good to go.
All 4 on my looper read 135 psi with one tester and 125 psi with a different tester. Which one is correct I do not know but motor is running great at present.