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Vacuum test on alpha 1 gen 2

Personally, I rely more on vacuum testing of lower units than pressure. If the seals leaks oil OUT the drive will keep functioning--it will run fine when half empty (or more)--but if the seals allow water to get in it's curtains! A vacuum test will tell you if water can be sucked in.

Jeff
 
Actually jeff you have it backwards.....
Water will lubricate temporarily where as if you go half empty on gear oil you will fry the bearing in the cap on the top of the upper case.

Pressure testing will confirm no oil will leak out...it does not always confirm water could get in.
If water is present in gear oil and the drive (empty) passes the pressure test then a vacuum test should be done. 4-8 inches is typical to expose a leak.
 
kghost said:
Actually jeff you have it backwards.....
Water will lubricate temporarily where as if you go half empty on gear oil you will fry the bearing in the cap on the top of the upper case.

Pressure testing will confirm no oil will leak out...it does not always confirm water could get in.
If water is present in gear oil and the drive (empty) passes the pressure test then a vacuum test should be done. 4-8 inches is typical to expose a leak.
Click to expand...
I know this is old, but where on the drive do you focus when doing a vacuum test?
 
If your drive is a gen 2, you have to pinch gear oil line to drive or remove drive from boat.

Drive gear oil must be drained before pressure or vacuum checks.

Once drive is empty then either the drain/fill (bottom of drive) or vent/level at top side of drive will work.

Typically you should see 4-6 inches/hg of vacuum. It should hold. If it does not you may have to seperate the upper amd lower cases to track down leak. If you have to do this, the oil passage hole in upper and lower must be plugged with a tapered rubber stopper when pressure or vacuum checking with cases seperated.

Why are you asking? Have you done a pressure check? Do you have water intrusion or gear oil leaking?
 
kghost said:
If your drive is a gen 2, you have to pinch gear oil line to drive or remove drive from boat.

Drive gear oil must be drained before pressure or vacuum checks.

Once drive is empty then either the drain/fill (bottom of drive) or vent/level at top side of drive will work.

Typically you should see 4-6 inches/hg of vacuum. It should hold. If it does not you may have to seperate the upper amd lower cases to track down leak. If you have to do this, the oil passage hole in upper and lower must be plugged with a tapered rubber stopper when pressure or vacuum checking with cases seperated.

Why are you asking? Have you done a pressure check? Do you have water intrusion or gear oil leaking?
Click to expand...
I had a oil leak from the right side water inlets and weap hole. I replaced the impeller and shift shaft seal. When I drained it, did have some water intrusion. Put it back together and ran it. Still water intrusion. Now I wish I would have replaced the seal carrier. I did inspect the prop seal, there was fishing line but didn’t look damaged. Going to drain, take the prop off and pressure test this morning.
 
Most likely the seal and oring assembly below impellor.
A pressure check would have revealed that. Pressure check to 15 psi and it should hold for a minute plus with no leak down
 
99% of the time a pressure check will reveal a bad seal or oring. When it doesnt then a vacuum check should be done.
 
Installed a new lower shift shaft housing when I replaced the impeller. Pressure tested and is leaking from the lower shift shaft. Is it a bad part or is something else causing it?
 
ToddMThayer said:
Installed a new lower shift shaft housing when I replaced the impeller. Pressure tested and is leaking from the lower shift shaft. Is it a bad part or is something else causing it?
Click to expand...
unless the shaft is galled or you forgot one of the orings under it yes its a bad part. Did you use a merc part or aftermarket?

given you had gear oil leaks out the water intake holes originally did you take the impeller back off and see if the shaft seal below it is leaking?

You can spray them with soapy water while pressure testing. Would be surprised if you snagged a fishing line and the seal wasnt damaged
 
Did you purchase OEM Quicksilver parts?

I recently did a shift shaft seal that was "For" a mercruiser purchased from amazon. It failed leak test immediately.
I had to run fo the near by Mercruiser shop and get a OEM. All was good after that.

Much of the equivilant parts for mercruiser are chinese knock off and fail.
 
ToddMThayer said:
No. So I guess replace the seal assy again and while it’s off, replace the lower water pump seal then retest.
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yes. Also with a merc shift shaft seal - they sell the plastic housing with the seal in (bushing assy) it and the seal alone... to save $10 I bought just the seal.... I could not get the seal to stop leaking in the old housing (bushing assy) even using permatex #3.
 
Bought a new housing from powerboat supply.
 

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