40hp magnum compression

[93’mariner40]

I have a 40hp magnum 4cyl 2 stroke, the compression test results were as follows
#1-94

#2-99

#3-97

#4-105

These numbers seem low, am I correct in thinking that. The motor seems to idle very well but stalls when put in forward. I also discovered that the carbs were both leaking, and the top carb vacuum line was broken off and not attached.

 

[faztbullet]

Check with different gauge

 

[93’mariner40]

I will have to get another one, the one I’m using is from o Reillys auto parts. Any suggestions on where to get a better one?

Also do you know if the vacuum line would cause the engine to stall when put under load?

 

[racerone]

What ----Vacuum line---Was it a hose from bottom of the float bowl ?----Open low speed mixture screws 1/8th turn at a time out oon the water.-----Often that will make the stalling go away.

 

[93’mariner40]

 

[93’mariner40]

I assumed this was a vacuum line but this T goes to each carb.

 

[faztbullet]

That is the primer choke

 

[93’mariner40]

Thank you for clarifying that!

 

[93’mariner40]

Is compression in the 90s really bad?

 

[93’mariner40]

the only manual I could find was the seloc and I thought I read in there a pressure of at least 90 was acceptable.

 

[faztbullet]

Selco manuals are good for emergency toilet paper at best. That motor should have a minimum of 100psi if worn out