vaccuum testing lowers

[outboardnut]

I know I need to start doing this. Plan on building a tester this winter.

Wondering what a good way to find vaccuum leaks on a lower?

With a pressure tester I usually just dump the lower in a tank and look for bubbles.

 

[Knightgang]

Re: vaccuum testing lowers

The only way to test with vaccuum would be like you do in a Auto A/C. Pull a vacuum and have a gauge attached. Leave sitting under the vaccum state for X amoutn of time and see of the vacuum holds. If there is a leak, it will not hold long. But I think pressure testing is a better option and more effecient...

 

[psteurer]

Re: vaccuum testing lowers

Here's a high quality and fairly cheap tool to pressurize and vacuum test lower units. You really need to do both for a lower unit. There is both an inside and outside seal and the lower unit might leak in only one direction. A MityVac 7000 costs about $30. For this particular model, the gauge will indicate vacuum pressure. You can see right away if it hold a vacuum or leave it on overnight. The gauge does not indicate air pressure. Dunking the lower unit in a tub of water will work for the pressure test but not the vacuum test. I also use mine for sucking and pushing crude out of carburetors.

 

[Knightgang]

Re: vaccuum testing lowers

That is good information right there. Where do you get that from???

 

[ezeke]

Re: vaccuum testing lowers

The MityVac 8500 has a dual gauge so that you can test both ways:
http://www.mechanicstoolsupply.com/...lverline-Elite-Automotive-Test-Kit/index.html

http://www.mityvac.com/pages/products_hvpk.asp

 

[jasper60103]

Re: vaccuum testing lowers

I know I need to start doing this. Plan on building a tester this winter.

Wondering what a good way to find vaccuum leaks on a lower?

With a pressure tester I usually just dump the lower in a tank and look for bubbles.

Mr.Stuart had a pretty good thread on this subject.
http://forums.iboats.com/showthread.php?t=320981&page=2

 

[wilde1j]

Re: vaccuum testing lowers

I made an adapter that threads into the drain hole, has a Schraeder valve and a tubing connection (to put a pressure/vacuum gauge on). I use a compressor for pressure and a MityVac for vacuum.

General testing procedure:
a) drain gear oil (it will mask leaks if left in)
b) pressurize (no more than 15 psig for v4/v6 LU's, less for smaller motors ... consult OEM shop manual. Higher pressures will blow out seals! You don't have to worry about vacuum ... it's OK to go to 30" Hg vac (that's equal to ~ -15psig) ... you just can't pull enough vacuum to do any harm to seals and 30"Hg is the max possible. For vacuum testing, I remove the valve core temporarily.
c) v4/v6 LU's should hold some pressure or vacuum for at least 45 minutes, smaller motors somewhat less time.
d) If leakage is found, submerge in water and look for bubbles for leak source
e) After repair, repeat pressure test (as a minimum) to verify repair.

For prop shaft or driveshaft seal replacement, if shaft is grooved where seal lip was, make sure to install new seal slightly offset to avoid any shaft grooving.

 

[outboardnut]

Re: vaccuum testing lowers

wow! lots of responces!

Should I excpent any less from this great forum?

Well I think my poor verbage is causing my orginal question and reason for thread unaswered.

I'm framiliar somewhat with vaccuum gauges and don't think I'll have to much trouble buidling one.

Question is, if I have a lower unit that pressures up fine and then fails a vaccuum test, how do I find the leak?

How do you telll where a vaccuum leak is?

 

[wilde1j]

Re: vaccuum testing lowers

If you submerge in water w/ vacuum, you will get bubbles also (and some water inside, which will need to be purged).