1983 merCruiser 3.0 4 cylinder.

[Austin9398]

I did a compression test and I found that I have 80 psi on three cylinders and 60 on the other the motor runs fine but want to know if the right or not

 

[Austin9398]

Have a weird noise coming from my 1983 merCruiser 3.0 4 cylinder kinda sounds like sucking air or something

 

[1985 Century Mustang]

Doesn't seem right. My Merc 3.0 is 165 160 155 and 150.

 

[1985 Century Mustang]

I did a compression test and I found that I have 80 psi on three cylinders and 60 on the other the motor runs fine but want to know if the right or not

Did you do the test correctly, something's off.

 

[Austin9398]

Doesn't seem right. My Merc 3.0 is 165 160 155 and 150.

I thought so but like I said it runs just fine no issues makes no sense

 

[Austin9398]

Did you do the test correctly, something's off.

I pulled all the plugs out then put the tester on the first cylinder then fired over 4 times the went down the line

 

[Scott06]

I pulled all the plugs out then put the tester on the first cylinder then fired over 4 times the went down the line

Suspect your gauge is off below 100 is normally A dead cylinder smoking like hell and tons of blow by.
if it runs good why did u do the compression check? Try with another tester

engine was up to temp ?

 

[ScottinAZ]

did you have the throttle set WFO.....

 

[1985 Century Mustang]

Can you take a video and post it? If you have a YouTube account you can take a video, post it to YouTube, and post the link. Getting a YouTube account is easy.

 

[Scott Danforth]

The GM 3.0 should be about 140-150 psi for a new motor as that is the published spec for cranking pressure.

As Scott said, anything below 100 is usually a dead cylinder

 

[Austin9398]

Suspect your gauge is off below 100 is normally A dead cylinder smoking like hell and tons of blow by.
if it runs good why did u do the compression check? Try with another tester

engine was up to temp ?

The temp was good oil pressure good it’s making kind of a hissing noise and that was the first thing I thought to do

 

[Austin9398]

Here is a video of what it’s doing

 

[Austin9398]

Can you take a video and post it? If you have a YouTube account you can take a video, post it to YouTube, and post the link. Getting a YouTube account is easy.

 

[1985 Century Mustang]

My guess: Sounds like you have a compression leak in the engine, not a vacuum leak. Suggestion: Go on YouTube and search videos for your same issue/sound/noise, see what you can come up with. Read all the comments if you find one similiar to yours. That's how I fixed my boat. I had a knocking noise by my flywheel. Some guy posted the same video, on YT. So it put me in the area that needed to be addressed. I pulled my engine and found a loose flywheel coupler. YouTube is an amazing animal.

My issue:

.

His issue: Almost the same sound.

 

[Scott06]

Spark plug not seated or exhaust manifold leak

 

[Bondo]

Spark plug not seated or exhaust manifold leak

Ayuh,..... Or a head gasket,.... Absolutely a compression leak,....