Compression test mercruiser 3lt

[m2bl3]

Hi all,

Been looking at how to do a compression test on engines.

So far I understand to do this test:

1. Seems you need the compression test gauge+hose and correct adapter.

Fit compression gauge in spark plug hole, turn engine 5 times and read the gauge.

2. Before the test is done I understand you need to disconnect the ignition from the engine to stop it firing. Also disconnect the fuel.

For 2. above does anyone know where the connections are located and how to disconnect them?

Cheers.

If you feel you can offer any further advice please do.

[mmwjr]

Additionally the engine should be warmed before performing the test.

On the ignition coil remove the wire from the positive terminal.

The fuel pump does not need to be disconnected.

[m2bl3]

Originally Posted by mmwjr

Additionally the engine should be warmed before performing the test.

On the ignition coil remove the wire from the positive terminal.

The fuel pump does not need to be disconnected.

Should be quite simple then.

Thank you

[stock333]

can someone let me know what is a good compression

thanks

mark

[mmwjr]

150 psi is normal and all cylinders should be within 10% of each other. Anyth8ng less than 110 psi is indication of an issue.

[m2bl3]

Originally Posted by mmwjr

150 psi is normal and all cylinders should be within 10% of each other. Anyth8ng less than 110 psi is indication of an issue.

Thank you for your reply. Very useful to know that under 110 psi is showing signs of problems.