454 Compression seems low but good power

[ALASKANESKIMO]

I have a 91 26' SleekCraft with a 330hp 454 a performer intake and a 780 cfm holley double pump carb on it. It gets out of the hole great and tops out at 50mph on the gps running 4600 rpm. I did a compression test on it just to check up on things and found most cyl. around 112-114 psi with the highest at 118 psi and the lowest at 102 with the throttle wide open and engine warm. I don't know exactly how many hrs are on it but from what the previous owner told me it is around 300 hrs. Is this compression getting low? Does being in Colorado make the difference? Thanks.

 

[magster65]

Re: 454 Compression seems low but good power

Howdy, I have a 1994 7.4 merc with 750 hours on it. I just did a compression test and they were 124 to 128 psi. My manual says they should be 140 to 150 psa when they're new. I'm not sure about how altitude affects a compression test.

 

[sony2001]

Re: 454 Compression seems low but good power

Yes, altitude does affect the compression, but the previous owner set it up well to be able to get 4600 rpm out of it.