Stern drive oil leak from upper

[Dschotts]

Hi,
New boat owner and new member here, although been lurking this forum for some time now (thanks for all the great info everyone!)

Recently picked up our first boat, a '91 Glastron 1900 with the 4.3 Mercruiser Alpha one Gen 2. Thanks to much of the information and links found on this forum we've completed most of the maintenance with the exception of the impeller replacement which I'm into now. The lower unit came apart quite smoothly and is sitting waiting for replacement parts on order.

Meanwhile, I noticed a fair amount of gear oil leaking at the back of the upper unit as soon as the lower unit came away, the oil is leaking out of a small orifice just above where the shifter "shoe" protrudes from the upper unit , Is this normal or is this a concern? What's odd is that there no evidence of an oil leak from there until I removed the lower unit.

Any advice would be greatly appreciated!
Thanks

 

[achris]

Could be nothing. When you reassemble the drive, do a pressure test. It's likely that ol is just 'spill' from taking it apart. The upper housing is sealed by the lower drivehshaft, and when you split the housings, quite a bit of oil leaks out and down onto the water pump area.

Chris........

BTW, swing your orientation around. The shift shaft is at the front of the drive. The propeller is at the back.

 

[Dschotts]

Could be nothing. When you reassemble the drive, do a pressure test. It's likely that ol is just 'spill' from taking it apart. The upper housing is sealed by the lower drivehshaft, and when you split the housings, quite a bit of oil leaks out and down onto the water pump area.

Chris........

BTW, swing your orientation around. The shift shaft is at the front of the drive. The propeller is at the back.

Hi Chris, thanks for response and correcting me on orientation (newbie here).

I will try to post a picture - I'm quite certain there is a specific point as described above in the front centred directly above the shift shaft that was oozing. Hope you're right but I checked it a couple times.

Thanks

 

[Dschotts]

No Title

Here's the view from the front looking back.

 

[Bt Doctur]

gear oil can only leak from there if the carrier seal is leaking oil into the bellows

 

[Bt Doctur]

http://www.boatfix.com/merc/Servmanl/14/14a4.pdf
See 4A-19

 

[achris]

Here's the view from the front looking back.

For oil to get there, it has to come from the exhaust cavity, and the only way that can happen is if the lower seals in the upper housing are leaking. And that means a full strip of the top housing. (did one for exactly the same leak about 2 weeks ago.)

Chris.........

 

[Dschotts]

Thanks Chris,
Although mechanically inclined and experienced, never worked on one of these beasts before. Two thoughts:

1/ Is it possible that if all the gear oil was not completely drained before removing the lower that some may have leaked into that area upon removal as part of that oil "spill" that occurs when pulling apart?

2/ Failing that, is there a post or resource for replacing the lower seals in the upper housing. Would you be able to briefly describe or point me in the direction on what a "full strip" is referring to and entails?

Many thanks!

 

[achris]

Did you remove the lower with the upper still on the boat? If so, then I suspect that's why you're seeing this 'leak'.... With the drive trimmed up, removing the lower will certainly allow oil to drop into that area of the exhaust cavity.

 

[Dschotts]

Did you remove the lower with the upper still on the boat? If so, then I suspect that's why you're seeing this 'leak'.... With the drive trimmed up, removing the lower will certainly allow oil to drop into that area of the exhaust cavity.

Chris,
Thats exactly the case, I'm going to finish the impeller service, re install the lower then have it pressure tested and take it from there. There was definitely water in gear oil so its now a case of hunting it down.
Thanks!!

 

[Rick Stephens]

To answer one of your earlier questions, what is entailed in replacing the seals in the upper gear case. The gear case is completely disassembled to access the lower seals. The lower seals are pretty easy once all the gears are out. The more difficult part is the input shaft seal just behind the u-joint yoke. To replace that seal will require a couple hundred in special tools to disassemble and then reassemble. The bearing pack is set with a rolling torque, which can be tricky the first time.

 

[achris]

Chris,
Thats exactly the case, I'm going to finish the impeller service, re install the lower then have it pressure tested and take it from there. There was definitely water in gear oil so its now a case of hunting it down.
Thanks!!

Can't pressure test with the drive installed. Must be removed from the boat.

 

[Dschotts]

Can't pressure test with the drive installed. Must be removed from the boat.

Meaning in order to best hunt it down test lower separately from upper? Or literally remove the entire stern drive assembly from boat ... confused. Appreciate some more clarity. Thanks Chris!

 

[Bt Doctur]

Has to be tested as a unit on the GEN II types. Did you drain the unit completely first?
Was the unit tilted or vertical when lower was removed?
Water in the gear oil can also come from a leaking bellows ,that you wont know untill you remove the drive or:
suffer drive failure
U joint exploding
Gimbal bearing coming apart

 

[achris]

Meaning in order to best hunt it down test lower separately from upper? Or literally remove the entire stern drive assembly from boat ... confused. Appreciate some more clarity. Thanks Chris!

Remove the complete drive. The lower can be plugged to pressure/vac test, but the upper relies on the lower drive shaft being in place to seal... Also, as BT says, pull the entire drive to inspect unis, gimbal bearing and bellows condition. Pull the entire drive EVERY year.(is a 10 minute job)

Chris......

 

[Dschotts]

No Title

Ok, all good and appreciated info. The bellows and gimbal were replaced in 2015 according to the owner and the receipt found in the file he passed to me. Visual inspection from below looks like bellows are new.

Completed the impeller replacement today and was reassembling when I noticed a guide tube was slightly deformed at one end. Should I replace this and/or be overly concerned?

 

[achris]

Looks like it's been run without water at some stage.... Check the exhaust shutters.

Chris......

 

[Dschotts]

Looks like it's been run without water at some stage.... Check the exhaust shutters.

Chris......

Chris, ok that sounds like my next chore. Meanwhile, is that upper guide tube even necessary? Conflicting info on this. Some saying it's only there for manufacturing.
Thanks

 

[Rick Stephens]

You don't have to replace the guide tube. All it does is help you align the water pipe when dropping the upper down onto the lower as it mates to the pump housing. Chris's point is that if you have heat deformation of the guide tube then that is a good indicator that at some point the drive was run with insufficient water and the exhaust overheated. When an engine is run without enough water the first thing that melts is the exhaust shutters, then the guide tube.

 

[Dschotts]

Thanks for calrification - good to know I dont need to delay putting it all back together waiting for a superfluous part :joyous: