Motor compression test

[SGV]

I have a 1988 150 XP it has 82 psi on 5 cylinders and 70 on the other is this acceptable for this age motor? This is cold engine pressure

 

[racerone]

Test with another gauge.------You have a bad gauge , blown head gasket or a motor with scored piston / broken piston rings.-----Remove cylinder head for inspection I say

 

[oldboat1]

Agree. With a different gauge and a little hope, test again. Then try a little two cycle oil in the 70psi cylinder and see if compression improves (actually, you might do that with all cylinders). Look for gauges in the cylinder walls, particularly the 70psi cylinder. Remove the exhaust cover to find damaged and broken rings.

 

[racerone]

Intake bypass cover is easier to remove and 1 gasket be a lot cheaper than the 2 exhaust cover gaskets !

 

[racerone]

One little gasket at $3.75 sounds better than 2 at $11 each I would say.

 

[racerone]

What was found on this motor ???

 

[Roadking57]

Does the op know how to use the compression gauge? Sounds like a one cycle reading.

 

[oldboat1]

^^yeah. Crank it over until the reading is fixed/needle no longer rises. Then record result.