1981 150 Evinrude Sport PSI

[cbcmarine]

So I have been reading lot's of threads and don't see one answer what compression should this motor be running when all is good? I have looked in the Manual and can't see it their either.

[tashasdaddy]

it is not a published item, due to the fact that compression guages all register differently. the rule of thumb, is over 100 psi, but more importantly, the readings are all within 10 % of each other.

[cbcmarine]

Great thanks so if I am running 120 that is not a big issue ? I was getting the opinion this was high by others. I thought this would be normal but I have mostly done car and snowmobile engines, so I am not sure how different they are.

[Benny1963]

most of the early to mid 1980s that i have checked crossflows that are runnng good but have some time on them usually pump mid to low 90s you
are looking for the 10% AREA BETWEEN CYLS .some of the 1980s
had low comp head gaskets .the one i just did with new rings fresh bores and stock thickness head gasket pushed 105 105 100 100 110 105 but the heads i had milled to the max trying to straiten them although milling the heads on a crossflow does nothing for the compression,
i considered this excellent although ive seen some stock 70 and early 80s
v4s in the 130s range

[tashasdaddy]

as long as they are within 10% you are great.

[Dhadley]

Actually you want no more than 15 lbs difference between high and low. The actual number depends on what heads and what head gaskets you're running. Be careful comparing a V4 crossflow to a V6 crossflow, they aren't the same.

Anytime you see numbers that are a little high you want to find out why. If the heads have been cut you might be headed for a disaster unless you do other things to compensate.

[Benny1963]

agreed i learned it fromwatching yalls post i wasnt meaning to compare the two ,the v4 crosflows i tested two of them were 130 range
the highest v6 ive seen was in the low 100s
it appears that the v4s have higher comp ratios
most of the post ive read on here for v6s seems 90s within 10% is normal

[Benny1963]

agreed i learned it fromwatching yalls post i wasnt meaning to compare the two ,the v4 crosflows i tested two of them were 130 range
the highest v6 ive seen was in the low 100s
it appears that the v4s have higher comp ratios
most of the post ive read on here for v6s seems 90s within 10% is normal