Mercruiser Alpha I Gen II drive leaking gear oil between housings

[Gunn]

Late last fall I pulled the sterndrive unit and replaced the water pump as preventative maintenance. So I had to remove the 6 bolts that join the drive shaft (upper) housing to the gear (lower) housing. Easy enough job...I've last did it a few years ago, no issues. Put it all back together and back on the boat.

Fast forward to last week and I took a look at the boat and underneath this sterndrive unit, the ground was dark colored. Sure enough I found some gear oil on the lower unit. I traced it up to the joint between the two halves. Somewhere between the midway point and to the forward end.

I wondered if maybe I forgot an o-ring or something that might go in the passageway for the gear oil, but didn't recall. Looked in the manual (steps 5-8, see attached) and there doesn't seem to be any gaskets between this joint. And I used a torque wrench to tighten all of the bolts to spec (except screw "C" which I think is an allen head bolt under the trim-tab zinc). So I don't think I missed anything.



What could be wrong?!

Tom

 

[BillK2632]

Most likely either forgot the o-ring (it’s called a quad seal) or it fell out somehow when you put the halves back together. They are very small and come with the water pump kits. Drain the gear lube before you take it apart again.

 

[Strecker25]

+1 on the quad seal, easy to forget.

I always pressure tested mine, even just for 10 minutes, before filling it back up with gear lube. You’ll know right away if you forgot or missed a seal this way

 

[Gunn]

Most likely either forgot the o-ring (it’s called a quad seal) or it fell out somehow when you put the halves back together. They are very small and come with the water pump kits. Drain the gear lube before you take it apart again.

Well...thanks! I am guessing I did indeed forgot to install it, as I don't really remember it at all. But then again it was back in November. (Un)fortunately, most of the gear lube as leaked out, so there probably isn't much more to drain! Now I just have to figure out how to get another quad seal, without purchasing an entirely new water pump kit.

Interestingly, I went back and read the manual again (the section "Water Pump Assembly - Installation" and no where does it mention this seal!? No wonder I forgot it.

+1 on the quad seal, easy to forget.

I always pressure tested mine, even just for 10 minutes, before filling it back up with gear lube. You’ll know right away if you forgot or missed a seal this way

How do you pressure test the outdrive? I have wanted to do this, but don't know how to go about it. That would have been great to do beforehand.

Thanks for the help!

 

[Gunn]

For reference, I found where the seal should have gone. Don't know how I missed it...

Part # 26-455771

 

[BillK2632]

You need a pressure tester, you can buy them pre-made or make one yourself from $15 worth of parts from Lowes. Basically it is a tube with a gearlube fitting on one end that connects to the gearlube vent hole. The other end has a tire valve and there is a guage connected to the tube with a T-Fittting. Plug it up, use a bicycle pump and put 15lbs in the drive (don't over pressurize it, you can blow out seals). Then leave it for an hour or two and make sure it holds pressure. Do this with the gear lube drained. If it does not spray soapy water around the input yoke, propshaft and shift shaft and look for bubbles. Google "outdrive pressure test" there are lots of articles and videos out there. It's a good practice to do the pressure test anytime you work on the drive - saves a lot of headache later.

And don't think you are the first person to forget the quad seal - I've done it - more than once. The pressure test caught it -- after the first time!

 

[Gunn]

Thanks @BillK2632 , I'm definitely going to build that!

 

[Strecker25]

Thanks @BillK2632 , I'm definitely going to build that!

I used to fill ours with 15psi and leave them all winter in our basement, never leaked. I think spec says they only need to hold 10-15psi for 1 hour though.

with the cost of haul out of something went wrong it gave me peace of mind before splash each spring.