Can a pressure test be performed on an Alpha 1 Gen II while it’s still on the boat

[Skidude17]

I have a drive that started leaking after I did some routine maintenance. I’ve already drained the oil. Can I do a pressure test while it’s still attached to the boat? Is the oil reservoir cap vented? Will the pressure blow any hoses off?

 

[harringtondav]

I'll weigh in with my thoughts. More sage thoughts to follow. The reservoir cap has a check valve that blocks pressure. That's how the thing works. And I'd guess the lube monitor tubes could hold the 10 ish psi from a pressure test.

But you're still ahead by pulling your out drive. You really need to periodically to check unis and your gimbal bearing. It's not a bad job. Just remember to shift your controller into full forward, and remove the speedo hose before pulling it. A transom sea kit is very inexpensive for the peace of mind you get.

The advantage of pressure testing the drive off the boat is you have confined any leaks to the drive. On your boat, you'll be guessing.

 

[Rick Stephens]

Agree with Dave. Too easy to pull a drive, 10 minute job. Much easier to see the seals and gaskets where a leak might occur and be able to spray soapy water or listen with a stethoscope or even just a piece of hose held to your ear.

 

[Skidude17]

I went ahead and pulled the drive. After about 5 minutes no noticeable leaks. I’m leaving it overnight to see if it stays. If there’s no change in pressure, what are the possibilities of where the oil is coming from. It doesn’t look like it was coming from where the drive mates with the gimbal housing. The oil was leaking off the drive prior to removal.

 

[alldodge]

Leak might not be the drive, could be the connection between drive and bell housing, hose and fittings to bottle.

How much pressure and have you tried a vacuum test?

 

[Skidude17]

Leak might not be the drive, could be the connection between drive and bell housing, hose and fittings to bottle.

How much pressure and have you tried a vacuum test?

I used 10 psi, and I have not done a vacuum test yet.

 

[Skidude17]

I put 10 psi on the drive. I haven't done a vacuum test yet, but the issue is oil coming out, not water coming in. Would I be able to track the leak location using a vacuum test?

 

[Rick Stephens]

Did you rotate all the shafts while pressurized?

 

[alldodge]

I put 10 psi on the drive. I haven't done a vacuum test yet, but the issue is oil coming out, not water coming in. Would I be able to track the leak location using a vacuum test?

Using both should show a leak it there is one in the drive

 

[harringtondav]

Most of the seals in that drive are double, back-to-back seals. Yoke shaft and shift rod seals are the exceptions. The dual seals prevent both internal pressure lube leaks, and external pressure water entry - mainly when your drive is cooling down. The outer prop shaft seal prevents water entry, and is the most abused seal in your drive.

So, like the others above said, you should also do a vacuum test to check the outer (water wet) seals.

Where on the drive does the oil seem to come from? What sort of maintenance did you do? Did you remove or disassemble the drive?

 

[Skidude17]

Where on the drive does the oil seem to come from? What sort of maintenance did you do? Did you remove or disassemble the drive?

I changed the impeller and impeller housing, so I did remove the drive, so it could be the oil path between the upper and lower drive unit. It looked like the oil is coming out of the weep holes on the front of the lower half of the drive, so that’s my prime suspect right now. I did a pressure test with the drive off, and it does seem to be losing pressure. Nothing visible, though.

 

[harringtondav]

I changed the impeller and impeller housing, so I did remove the drive, so it could be the oil path between the upper and lower drive unit. It looked like the oil is coming out of the weep holes on the front of the lower half of the drive, so that’s my prime suspect right now. I did a pressure test with the drive off, and it does seem to be losing pressure. Nothing visible, though.

I don't want to jump to conclusions here. But since you have your drive off the boat, split it again and see if that quad ring seal is in place. If missing it will dribble lube on the floor, or back into the lower gear housing where it will show itself through a couple different weep holes.

Aside from splitting it again, it's a cheap fix. Merc p/n 26-45577 1, or Sierra 18-2944. Shipping will cost more than the seal.

I clean up the counterbore seat in the lower case with mineral spirits, and tack the seal in place with a small touch of contact cement.

 

[Rick Stephens]

The other two places that will leak from the weep holes are under the water pump housing, there's a seal in there where the shaft enters the lower case, and the output shaft at the bottom of the upper case. I had an output shaft that was leaky and the only way I found it for sure was to tip the drive upside down and fill that with it tilted just right with soapy water mix and watch the bubbles. The water pump seal is a little tougher since the air will come out the pump vent hole. Fairly easy and cheap to replace though.

 

[QBhoy]

Hi
likely thinking too simple, but did you disconnect and reconnect the header reservoir tank lines properly for the gear oil ? Many forget and damage the line or fittings when removing the drive. Done it once myself. Never since. Haha.

 

[Skidude17]

I found the leak, and it was at the shift shaft seal. The seal is replaced, and it holds pressure. I spun the shift shaft and the drive shaft, and both seals hold. They do release pressure when I put lateral pressure on them. Is that normal?

 

[alldodge]

Lateral as in side to side, then things are worn (bushings, bearings) at least what I'm thinking

Propeller Shaft
INSPECTION
1. Inspect the propeller shaft for side to side movement, as follows:
a. Position the dial indicator on the propeller shaft.
b. Push the propeller shaft to one side and zero the dial indicator.
c. Move the propeller shaft to the opposite side while observing the dial indicator.A
shaft deflection of more than .003 in. (0.08 mm) indicates a worn propeller shaft
bearing.
2. Check for a bent propeller shaft as follows:
a. Rotate the drive shaft in gear while observing the dial indicator. If the deflection is
more than .007 in. (0.178 mm), a bent propeller shaft is indicated.

 

[Skidude17]

Lateral as in side to side, then things are worn (bushings, bearings) at least what I'm thinking

Propeller Shaft
INSPECTION
1. Inspect the propeller shaft for side to side movement, as follows:
a. Position the dial indicator on the propeller shaft.
b. Push the propeller shaft to one side and zero the dial indicator.
c. Move the propeller shaft to the opposite side while observing the dial indicator.A
shaft deflection of more than .003 in. (0.08 mm) indicates a worn propeller shaft
bearing.
2. Check for a bent propeller shaft as follows:
a. Rotate the drive shaft in gear while observing the dial indicator. If the deflection is
more than .007 in. (0.178 mm), a bent propeller shaft is indicated.

It’s not the prop shaft. It’s the drive shaft and the shift shaft. The prop shaft doesn’t move at all.

 

[alldodge]

Drive shaft should not move
Shift shaft, might need a new bushing and seal (items 34 and 36)

https://www.mercruiserparts.com/bam/subassembly/30858/1017/80

 

[Skidude17]

I just put a new seal (36) on the shift shaft. Item 34 is just a sleeve that acts as a spacer, and wouldn’t limit any movement. I wonder if the drive shaft has some wiggle because it’s not attached at the top when the drive is split.

 

[achris]

It's normal for the drive shaft to have a bit of lateral movement when the housings are split. The drive shaft bearing in the lower housing faces up, so the bearing only seats properly when the drive shaft is subject to a force pushing it up. That force is provided when the gears are being turned under load. They try to force themselves apart, thus pushing the drive shaft up. Because there is a clearance (called backlash) between the pinion and forward/reverse gears, the shaft will drop down when there's no load., and the tapered roller bearing will separate from its race, allowing a small amount of lateral movement.

The older MC1 and R drives (pre-1982) had the bearing facing down, and to provide the downward force a spring loaded pin was added to the top of the drive shaft. The pin pushed up into the bottom of the upper drive shaft to provide the constant down force. I find it both unbelievable and a display of a complete lack of understanding of how things work, when people putting an older 'preload pinned' lower housing in place of a later one, cut the pin off because the newer drive shafts don't have a pin. Just :facepalm:...

Chris.....