[JoeDoyle]

Hi guys, just looked at a nice z272 Barchetta and I'm ready to buy. Got the compression test results from the mechanic and wondering what your opinions are. Here is the info:

7.4 liter Mercruiser, 630 hours on hull, seller claims a remanufactured motor was put in about 350 hours ago, no supporting paperwork provided

Ran at cruising speed for about 30-40 minutes on and off before the test. Boat ran spectacular!

All cylinders tested at 120 psi except for #1 cylinder which was 125 psi

Very good grouping but I need an opinion about the 120 psi, is that too low? I cant find much on the internet but I have found a couple of places that say this engine should be around 140-160 psi.

Any chance the seller could be lying about the reman motor and that this is the original motor with 630 hours? I have also heard from a mechanic that each motor has different characteristics and that 120 is a good reading as long as all cylinders are within 10%.

Can this compression test tell me anything about how much life to expect out of the motor?

This is a great forum and I appreciate any feedback from you guys! Hopefully soon I will be a true Mariah owner!

[mikeyt]

Those numbers sound fine Joe. Anything over 100lbs and consistent between the cylinders indicates a good engine compession and ideally it should be somewhere between 125 & 150 on a new engine. My understanding though is that compression checks should be done with the engine cold rather than run for a while. Hot checks would read slightly higher than a cold check. Is the seller the person who installed the remanufactured motor? At least he could tell you where the motor was purchased from & who did the install work.... the 454 should get up to 1000hrs on it before needing a top end rebuild.

[warner0308]

as long as its within 10% you should be all wright! compression test should be done at wide open throttle. And that could be a cheap compression tester, harbor frieght, some 20.00 dollar tester.