Bad Compressions on 2000 7.4L MPI

ni7irs

Seaman
Joined
May 2, 2010
Messages
60
Last summer my boat lost a lot of power. It could barely stay on the plane with five people aboard whereas the summer before we could have ten.

I did a compression test (badly) and almost all of the cylinders showed about 50 except one which was 90. The boat has been in storage now for the entire winter and was a little cold when I did the test. Admittedly, I did not open the throttle to full open when doing the test, but would this make up the 50 psi I need to meet the minimum 100 psi the service manual calls for?

Assuming the worst, what are my options? Can I install a new set of larger rings?

I see some places advertising rebuilts at about $3,000, but it looks like I have to reattach pretty much everything to the engine.

One place seems to advertise that I can increase the horsepower on the engine. Is this true?

Thanks in advance for counsel!
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Bad Compressions on 2000 7.4L MPI

Start it up, run it for a couple of minutes then do a compression test. If you only had 50 lbs, it wouldn't even run.
And when you do the compression test, pull the kill switch to disable the ignition and fuel pumps.
There are a lot of things that could cause your problem that do not require a new engine.
 

ni7irs

Seaman
Joined
May 2, 2010
Messages
60
Re: Bad Compressions on 2000 7.4L MPI

Start it up, run it for a couple of minutes then do a compression test. If you only had 50 lbs, it wouldn't even run.
And when you do the compression test, pull the kill switch to disable the ignition and fuel pumps.
There are a lot of things that could cause your problem that do not require a new engine.

Thanks Don!
 
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