Lower Unit Vacuum Pressure Test

I just performed a pressure and vacuum test on my lower unit and I'm having trouble interpreting the results. Can someone help me out with this?

1968 Merc 1250 125hp Inline 6 - New drive shaft seals only.

Pressure Test: Held 15 psi overnight (actually went up as it got warmer). Held 6 psi for 2 hours with zero leakdown.

Vacuum Test: Put 15 hg and it leaked to 8 hg in two hours. The next hour down to 7.5 hg, which is where it is right now. Tried putting the oil in suspect places, but couldn't tell if it was getting sucked in or not.

My manual says do it at 15 and if it "holds" at 15 then do it at 6. If it "holds" at 6, then it's good. It does not give a time limit for holding, so that's where my confusion lies.

Thank you,
Mark

Re: Lower Unit Vacuum Pressure Test

I rebuilt mine last year and asked the same thing and this is the answer i got and my LU has been fine

http://forums.iboats.com/mercury-mariner-outboards/vacuum-pressure-test-586948.html

Re: Lower Unit Vacuum Pressure Test

MH Hawker said:

I rebuilt mine last year and asked the same thing and this is the answer i got and my LU has been fine

http://forums.iboats.com/mercury-mariner-outboards/vacuum-pressure-test-586948.html

Click to expand...

Thanks MH

Re: Lower Unit Vacuum Pressure Test

WOW, I just went through that same test on my lower foot. And I too had the same question as to how long should you wait to verify it holds pressure. So I had mine hold for an hour or so and called it quits. Of course I had to go into it eight times before I got it to hold 16PSI pressure. As for the vacuum leaking, the seals you installed are to keep oil in and if you look closely you would see the lips on those seals are pointed inward. So trying to pull air in will get by those seals easier then applying pressure... JMHO!