Lower Unit Leak Test 1963 75hp

[yorab]

Motor in signature. I've got the LU back together and I want to leak test it before putting back onto the motor. I've searched the forums and read some conflicting numbers. I just want a definite vacuum gauge reading for my particular motor. I also read about back to back seals in the water pump area, but I don't believe that this applies to my motor.

I have a Mitymac vacuum gauge but not a pressure gauge. I could buy the pressure gauge attachment for it if it is absolutely necessary.

My questions: will a vacuum test only be sufficient to test for leaks (again, for my particular motor)? What vacuum level should I pump to? Thanks.

 

[wilde1j]

Re: Lower Unit Leak Test 1963 75hp

The most vacuum you could possibly get (30" Hg) ain't going to happen, so don't worry. You need to pressure test as well (=< 15 psig). A ggod lower unit will retain some pressure for 45 minutes. If it's leaking, put under water and look for the bubbles. BTW, drain the gear oil before testing.

Pressure test is more important than the vacuum test. A bicycle pump can handle that fine.

 

[yorab]

Re: Lower Unit Leak Test 1963 75hp

Ok. I'll try the pressure test at 15 psi. The Mitymac pump that I have will create pressure, but the gauge won't read the value. It only reads vacuum. They make an attachment gauge for that hand pump and I'll try to get it. Otherwise, I have some gauges around and I can try to rig something up. My biggest concern is pumping the pressure too high and blowing a seal.