Compression on 2011 242 Limited S with 250 Hours

[lifeisradincbad]

Compression test performed at local Yamaha dealer.
Port: 145, 125, 140, 145 psi
Starboard: 150, 125, 120, 150 psi
What's normal? Any concens with these readings? Too low? Inconsistent?

 

[Dave burke]

A little inconsistent but not that worrisome to me. But I haven't tested mine so I'm not totally sure,

Why did you do the test? Are the engines running well?

 

[FSH 210 Sport]

Compression test performed at local Yamaha dealer.
Port: 145, 125, 140, 145 psi
Starboard: 150, 125, 120, 150 psi
What's normal? Any concens with these readings? Too low? Inconsistent?

Id have a look at what the service manual states the compression should be and what the variances should be. See post #3 from @Scottintexas showed for the mr-1 engines. I would think the service manual for the engines in question would have the same information.

I think variances over 10% need to be looked at closely, the low numbers should be at 130 or above for the port engine, and 135 for the starboard. Was the starboard engine engine tested first?

Was the engine tested warm? Did the person performing the test try squirting some oil into the cylinders to see if the pressure increased indicating piston ring leakage? Perhaps checking the valve lash would give a clue as to where the compression losses are.

https://www.motortrend.com/how-to/engine-diagnosis-leakdown-compression-test/

 

[David Martin]

Not overly concerned with the 120 and the 125 but it would be enough for me to do some further testing/investigation. Several reasons for low compression on just a couple of cylinders................One could be ring wear and lost compression on those cylinder but usually ring wear is consistent on all cylinder's . A second is fuel injector corrosion that changes the normal gas spray pattern to a more of a gas stream ..........this gas stream and poor ignition of the gas washes the oil off the cyl walls and the rings causing a dry cylinder that will check as low compression.

You needed to look/read all the plugs to see how the engine is firing.............the plugs could be extreme rich (black plug) wash down condition or EXTREAMLY LEAN CONDITION drives the piston/cyl temp up high and causes the oil to be removed from the walls to quick...... allowing higher wear than normal and causes low compression test because of a dry cyl.

Read the plugs Thay will tell you how the engine is doing and it might just give you the info needed to correct and problem before it to late.