5.0 Mercruiser compression readings

[saltwater_cowboy]

Friend just got a new boat with this engine.<br /><br />I ran the test with the engine cold.<br />6 cylinders at 155 Psi<br />1 at 140<br />1 at 130<br /><br />Anything to worry about? The 2 lower readings were not next to each other and both went up with a little oil in the bores.<br /><br />Carb is all messed up and gunky so have stripped that and soaking it.<br />Will rebuild and test at the weekend.

 

[waterone1@aol.com]

Re: 5.0 Mercruiser compression readings

From your post it would indicate that this is a piston ring issue. These readings are not real bad, so I would have to question how long it has been since this engine has been run ? How many hours are on this engine ? In my opinion, this could be a sign of trouble, or it could be an engine not fully broken in, or one that has set for some time ?? I would run the engine for a few hours, then repeat the test. Please give us some more info .

 

[saltwater_cowboy]

Re: 5.0 Mercruiser compression readings

Hi,<br /><br />Engine had sat unused for 3 - 4 years.<br />I've run it for less than one hour and it idled ok but stalled under load.<br /><br />Carb has since been striped and being rebuilt to solve stalling problem.<br /><br />Do you think the 2 low cylinders will pick up with some more use.

 

[waterone1@aol.com]

Re: 5.0 Mercruiser compression readings

If you haven't already done so, replace the oil and filter, next I would proceed with the carb work and any other needed tune-up items, then run the boat under load for a few hours. Keep an ear out for any unusual noises or smoking. Then repeat the compression test.