Compression on 98 Merc 5.0?

wetcat

Recruit
Joined
Sep 11, 2003
Messages
4
I have a 1998 Merc 5.0 305 carb. engine with about 150 hours. I did a compression test on one cyclinder on each side. Tested at 90 and 95 lbs. Does this sound about right.
 

Skinsk

Petty Officer 2nd Class
Joined
Aug 31, 2003
Messages
128
Re: Compression on 98 Merc 5.0?

Did you have the carb held wide open? Was the engine cold? <br /><br />Those readings seem low to me.<br /><br />Scott..
 

wetcat

Recruit
Joined
Sep 11, 2003
Messages
4
Re: Compression on 98 Merc 5.0?

It was a little warm. Carb throttle was not opened. Also ran engine 30 seconds with tester hooked up and got the same readings as when I just turned it over. What is the normal range compreesion for this engine? Thanks.
 

CCrew

Chief Petty Officer
Joined
Sep 10, 2003
Messages
416
Re: Compression on 98 Merc 5.0?

I'd expect to see 120-125 with the throttle plate open. It needs to be full open with all the plugs out to get the most accurate readings <br /><br />What you're looking for most is equality across all cylinders in the pressure readings, rather than the highest #<br /><br />Hope that helps!<br />Roger
 
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