Test Lower Seals for Leaks

[HONKER1]

I have read several posting on testing the lower unit for seals leaking. I have a '01 115hp 2-stroke motor. I was changing the gear lub and noticed some, about a soup spoon size, of light brown fluid mixed in with the dark green lub. Decided to test the seals with a vacuum test, but can find the amount of vacuum I need to hold for the test. I did find I need no more then 10 pound of air pressure. but how many Inches of Mercury should I be pulling.
I am pulling 20" of Mercury now, should it be more or did I already damage something?

 

[Laddies]

Re: Test Lower Seals for Leaks

I have justed check several of my OEM manuals and can not find any specs for vacuum or for that matter pressure, we use 10 & 10 for 1 hour with 0 leak down if that helps at all.

 

[HONKER1]

Re: Test Lower Seals for Leaks

Thanks Laddies for the reply. I had the 20" of mercury on for over 20 hours. It dropped from 20" to 8", but I'll bet it held 20" for 1 hour. I've never learned how to test for a vacuum leak, other then spraying with soap to see if it gets sucked in. Just watch the gauge to see if it drops. Any leak could also be in the gauge setup. We are dealing with such a small volume of vacuum.
Now need to re-invent the wheel and make a 10# air pressure setup.

 

[Motor Boater Bill]

Re: Test Lower Seals for Leaks

I made an adaptor for a standard air hose fitting to go in the LU drain hole, then I put the amount of pressure I want in my portable tank, hook it up, open the valve on the tank, then close it again. Open the valve again later and see if any air moves in--if so, it leaks, look for bubbles. If you use too much pressure you can make a bad seal actually push tight and seal up even though it's bad, so some recommend testing at lower pressure like 5 psi also.