Pressure Testing Alpha 1 Gen 2? Vacuum too?

[enginesilo]

Is it ideal to only do a pressure test, or should I plan to do a Vacuum test too? I already read the sticky but there wasn't a ton of specifics.

I was planning on building a simple pressure tester, but may opt for a gauge with pressure and vacuum if its ideal to do the vacuum test too. My plan was to build it and then use a bike pump for the pressure end, and use a brake bleeder for the vacuum.

I saw some oil drip out of my weep hole in my Alpha 1 Gen 2 drive last year so I want to do a pressure test while its still winter. I took the drive off and have it ready to test as 1 piece, and I then plan to separate the top and bottom and test them separately.

Any tips on if Pressure and Vacuum should be done appreciated.

 

[NHGuy]

I just rigged a simple valve to a piece of clear tubing on a fill pump tip. Pumped it to 13 psi and watched for a few hours. When I found it leaking I then put a little soapy solution around things til I found bubbles. Easy. I have a hand vacuum pump so I attached that too. The vacuum test really isn't that important, but do it if you can.

 

[enginesilo]

I just rigged a simple valve to a piece of clear tubing on a fill pump tip. Pumped it to 13 psi and watched for a few hours. When I found it leaking I then put a little soapy solution around things til I found bubbles. Easy. I have a hand vacuum pump so I attached that too. The vacuum test really isn't that important, but do it if you can.

Thanks for the tips. I'm going to rig something up. If I plan to do Vacuum i'll buy a different gauge but I'm thinking I may just do a pressure test for now.

 

[Fun Times]

Reading the forums there's mixed emotions if a vacuum test should be done or not. Some manufactures recommend it while others do not.

Mercruiser does not recommend a vacuum test in their service manuals due to the type of yoke seal on most of their input shafts.

1. Drain gear lube and install lower drain plug.

2. Remove vent plug and install pressure tet gauge. Tighten securley

3. Presureize housing to 7=10 psi and observe gauge for 5 minutes.

4. Rotate drive shaft, prop shaft and move shift rod while housing i pressurized to check for leaks.

5 Pressurize housing to 15-16 psi and observe gauge for 10 to 15 minutes.

6. Rotate drive shaft, prop shaft and move shift rod while housing i pressurized to check for leaks.

7. If pressure drop is noted, immerse housing in water (or use liquid soap and water mixture).

8. Repressurize to specification and check for air bubbles.

9. Replace leaking seals as necessary. Retest housing.

NOTE: Vacuum tests are not recommended due to the design of the labrinth seal (will not hold vacuum.)

10. Remove tester from housing, fill with lubridcant and install vent/drain plugs.

The labrinth seal on the input shaft is designed to keep the oil in the drive while the u-joint bellows is supposed to keep the water out of the drive.

That mentioned, some have done low vacuum tests on Mercuiser drives successfully for a better peace of mind. It'd be best to stay under 7 in Hg though should you decide to do it.

 

[enginesilo]

Reading the forums there's mixed emotions if a vacuum test should be done or not. Some manufactures recommend it while others do not.

Mercruiser does not recommend a vacuum test in their service manuals due to the type of yoke seal on most of their input shafts.



That mentioned, some have done low vacuum tests on Mercuiser drives successfully for a better peace of mind. It'd be best to stay under 7 in Hg though should you decide to do it.

Thanks again for the specifics. So step 5 says 15-16psi? I always see people saying don't go over 12psi or you'll do damage. Are these steps the safe ones to follow with an Alpha 1 Gen 2? Should I even bother doing a vacuum test? If Mercruiser doesn't recommend it I may just skip it.


I went to Home Depot with hopes of buying some of the parts I need to build my pressure tester and they hardly had a darn thing, my Home Depot in particular is a high volume store and the selection is crappy. Was thinking maybe I'd just bite the bullet and but a MityVac that has the gauge and pump build right in, and just throw the metal fill adapter on the end of the tubing for a quick build. Going to try a plumbing supply and Amazon before I give in.

 

[SDSeville]

Thanks again for the specifics. So step 5 says 15-16psi? I always see people saying don't go over 12psi or you'll do damage. Are these steps the safe ones to follow with an Alpha 1 Gen 2? Should I even bother doing a vacuum test? If Mercruiser doesn't recommend it I may just skip it.


I went to Home Depot with hopes of buying some of the parts I need to build my pressure tester and they hardly had a darn thing, my Home Depot in particular is a high volume store and the selection is crappy. Was thinking maybe I'd just bite the bullet and but a MityVac that has the gauge and pump build right in, and just throw the metal fill adapter on the end of the tubing for a quick build. Going to try a plumbing supply and Amazon before I give in.

I made my pressure tester with stuff mostly from the auto parts store. In-line fuel pressure gauge ($15), fuel line ($4) and rubber valve stem ($2). I used the metal end of my outdrive oil fill pump to complete it.

 

[UncleWillie]

Don't confuse the Alpha One (Legacy) with the newer Alpha One Gen 2.
The older Alpha was a sealed unit that built up pressure when it warmed up while operating and formed a vacuum when it cooled off to a temperature lower that it was when it was last sealed up.

The Gen 2 is vented through the reserve bottle and never see any pressure or a vacuum.
The worse it will see is when sitting on the trailer with the drive down.
The lower unit will see about 1.5psi from the 3 feet of oil column. Even less pressure when in the water.
Unless you forgot to install all the o-rings, it will very hard to get a Gen 2 to leak. And if it does, it will be a leak Out!
If it will hold 5 psi for 10 minutes, you are more than golden.

 

[enginesilo]

Thanks for the feedback everyone. So I built myself a pressure tester and I did some testing this weekend. I can use some help and greatly appreciate any feedback you can all share. I am pressure testing because my boat had some oil dripping out the drain/weep hole on the starboard side of the outdrive, and it seemed like it was running slightly hotter than normal. I drained the oil and there was no oil intrusion at all. Here are my pressure test findings.

Pressure Testing Upper and Lower as 1 unit
The drive held 12psi for a bit, but within 30 minutes it had dropped to 10psi. I sprayed around the drive and found the shift shaft seal/bushing was leaking very slowly. If I understand from the manual I buy the entire bushing piece that has gaskets and I replace the entire thing. The manual didn't mentioned it, but on the web I found people saying to put it in forward and then lock up the prop so it can't pop out of gear. Sounds reasonable, I am going to try it. Any other tips appreciated.

Pressure Testing Lower Unit
Same as above, I found that the shift shaft seal is leaking and will be changing that. I also noticed that if I touch the drive shaft, air will escape around the Oil Seal Carrier. But if I don't touch the drive shaft at all, no air or oil escapes from the oil seal carrier. Is this normal and how it should be functioning?


Pressure Testing Upper-Need Help
I'm not exactly sure how to pressure test the upper, can someone share some tips? I tried to block up the oil passage but could hear the air hissing out of where the drive shaft mates into the upper. So i'm guessing i'm doing it wrong. When I separated my upper from my lower I got a good 1/2 cup of oil that was dripped down the drive shaft onto the impeller housing and close areas. Could this mean my upper seals are bad? Or is this supposed to drip like this? I don't remember it doing this years back when I changed my impeller. What are symptoms of needing your upper seals redone? I did not have any oil in my bellows, just when I separated the upper from the lower did I get all the oil down the driveshaft.

Thanks

 

[UncleWillie]

When you separated the upper unit , you opened up the hole where the drive shaft attaches.
Any residual oil in the upper is going to drain out. Completely expected and normal.
To test the upper, you will deed a sacrificial piece of drive shaft to fill in for the lower unit and a way to hold it in place under pressure.

Realistically there is no reason to test the upper while detached from the lower.
When you attach the two together you will need to retest again because the actual drive seal and oil passage ring have not been confirmed.

There is no reason you should have to Baby the drive to get it to not leak.
It should not leak with the shifter or prop shaft in any position or under any load.
You should be able to shift in to forward or reverse and spin the input shaft to rotate the prop without any leaks.
That is how it is going to be operated at all time the engine is running.

 

[enginesilo]

When you separated the upper unit , you opened up the hole where the drive shaft attaches.
Any residual oil in the upper is going to drain out. Completely expected and normal.
To test the upper, you will deed a sacrificial piece of drive shaft to fill in for the lower unit and a way to hold it in place under pressure.

Realistically there is no reason to test the upper while detached from the lower.
When you attach the two together you will need to retest again because the actual drive seal and oil passage ring have not been confirmed.

There is no reason you should have to Baby the drive to get it to not leak.
It should not leak with the shifter or prop shaft in any position or under any load.
You should be able to shift in to forward or reverse and spin the input shaft to rotate the prop without any leaks.
That is how it is going to be operated at all time the engine is running.

Thanks for the specifics, its helpful since the manual doesn't give some details, and online there is such a mix of info.

So it sounds like my upper oil leak might be normal, that's cool. So my plan is to fix the stuff on the lower that needs it, reassemble, and then test again and hope it all holds.

So with the oil carrier seal, if you move the drive shaft say 5 degrees from straight up, it should not leak? I'm assuming it is the oil carrier seal that needs replacing? Here is a YouTube video that shows the same leak, only difference is if I don't touch my drive shaft it does not leak at all, and only leaks if I touch it and slightly move it out of alignment:
https://youtu.be/ok6n2hVNf0g

So if I change the oil carrier seal should it take care of that issue then? I had some oil in the underside of the impeller housing near the oil carrier seal, so i'm thinking it is shot.

I read in the manual that you need a special tool to push the oil carrier seal back down, but this guy on YouTube used a wrench with success. Is this ok to do?
https://youtu.be/OuilMAOMpgQ?t=7m54s

Thanks for the help!

 

[UncleWillie]

I think you are creating your own problems. :joyous:
The upper oil leak is completely expected.
It is like complaining that your oil pan leaks whenever you remove the drain plug. :doh:

If you push the drive shaft out of alignment, any seal is going to leak.
In normal use, it is accurately centered.
What I meant was, anything that happens in normal operation should not make it leak, turning the shafts and shifting the gears, etc.
Testing the units while apart is problematic as you have found, and will not guarantee that they will not leak when mated together.

A common problem spot, is the oil passage that connects to the Gimbel Housing.
The valve is only there to prevent making a mess while the drive is off the boat.
The valve is Open 100% of the time the drive is installed and may not give a perfect seal for pressure testing.
It serves no purpose other than allowing the mechanic to lay the drive on its side and not make a mess.
It is strictly a convenience item and not required for normal operations.
If you find it leaking, don't worry about it.

 

[enginesilo]

I think you are creating your own problems. :joyous:
The upper oil leak is completely expected.
It is like complaining that your oil pan leaks whenever you remove the drain plug. :doh:

If you push the drive shaft out of alignment, any seal is going to leak.
In normal use, it is accurately centered.
What I meant was, anything that happens in normal operation should not make it leak, turning the shafts and shifting the gears, etc.
Testing the units while apart is problematic as you have found, and will not guarantee that they will not leak when mated together.

A common problem spot, is the oil passage that connects to the Gimbel Housing.
The valve is only there to prevent making a mess while the drive is off the boat.
The valve is Open 100% of the time the drive is installed and may not give a perfect seal for pressure testing.
It serves no purpose other than allowing the mechanic to lay the drive on its side and not make a mess.
It is strictly a convenience item and not required for normal operations.
If you find it leaking, don't worry about it.

Thanks Uncle Willie,
All very helpful. I'm definitely not going to mess with the upper unless it shows some type of issue once all back together. So let me ask more about that oil carrier seal assembly, the one that is below the water pump housing. Last season I had a small amount of gear oil dripping out of the starboard side weep hole. I also had gear oil in the impeller and below it near the oil carrier seal when I pulled it apart for the pressure test. Think this was caused by the shift shaft seal leak? Or could this be a sign that the oil carrier seal is also bad? I was loosing about 1/2oz-1oz every boat ride towards the end of last season, but when the boat was on the trailer I only got a little bit of dribble out of the weep hole, and there was no water in the oil at all. I can't imagine the shift shaft seal was doing all of that leaking, but I guess it could.

Now that I have the drive apart, I'm just trying to figure out what I should change to hopefully resolve the leak once and for all.

 

[UncleWillie]

As long as you have come this far you might as well replace any seals that you even think might be leaking.
The effort it takes to get the drive back Off the boat and then back on again after you notice a leak, is just not worth the very small amount of expense that replacing a seal costs.
The piece of mind of a season of boating without loosing a drop of oil will more than make up for it.

Mercury has a special tool to install every part they make.
This is perfectly valid for use on an assembly line where the tool saves 17 seconds of labor and is used 100 times a day.
For the garage mechanic where time is not at a premium, many alternate methods work just fine.
As long as you get the old seals out without damaging the drive casing, and get the new seal installed straight, that is all that counts.
Pushing in a seal is often a matter of just finding a washer with the right size hole in it to circle the shaft.
Or drilling a hole in a piece of scrap metal or wood will allow you to push it in evenly.
Often the old part makes the perfect tool to use to install the new part.

A few dollars spent now is highly recommended.

 

[enginesilo]

As long as you have come this far you might as well replace any seals that you even think might be leaking.
The effort it takes to get the drive back Off the boat and then back on again after you notice a leak, is just not worth the very small amount of expense that replacing a seal costs.
The piece of mind of a season of boating without loosing a drop of oil will more than make up for it.

Mercury has a special tool to install every part they make.
This is perfectly valid for use on an assembly line where the tool saves 17 seconds of labor and is used 100 times a day.
For the garage mechanic where time is not at a premium, many alternate methods work just fine.
As long as you get the old seals out without damaging the drive casing, and get the new seal installed straight, that is all that counts.
Pushing in a seal is often a matter of just finding a washer with the right size hole in it to circle the shaft.
Or drilling a hole in a piece of scrap metal or wood will allow you to push it in evenly.
Often the old part makes the perfect tool to use to install the new part.

A few dollars spent now is highly recommended.

Thanks again for all the tips. I will be changing this out while I'm in there as well.