Alpha 1 Gen II gear lube leak, pressure test

[1coolguy]

Hi, I've got a 1997 merc alpha 1 gen II, with a merc 350. Just noticed quite a large gear oil leak that appears to be coming from what looks like a couple of weep holes on either side of the top of the lower unit. When I raise the outdrive, it appears to leak from around the gear shaft bushing. I suspect that the oil seals just below the water impeller are leaking, but from what I've read on here it seems that I probably should pressure test the stern drive. I've looked through my shop manuals and can't find anything regarding pressure testing. It seems rather simple to pressure test, but I'm confused about a couple of things that I can't find elsewhere on here. My outdrive has the square bottle for gear lube located within the engine compartment. Once I drain the outdrive and start to presure test, won't the pressure just escape through that bottle? Am I supposed to remove the outdrive before presure testing? If so, how do you plug the hole that leads to that plastic square bottle? Also, I'm guessing that I'm probably going to have to pressure test the lower unit sepparately, and possibly the upper unit also, so that I can see where it's specifically leaking from. Again, how do you plug the oil passage that leads to the upper unit, and vise verca?

Also, by the way, I was looking at the service manuals under the Don S link and can't find the proper manuals for 1997 merc 350. It appears that the one I need is #17, but when I try and download that, all I get is the first 6 pages of Book 2 of 2. Does anyone have a link to the full maunal?

Thanks

 

[Uraijit]

Re: Alpha 1 Gen II gear lube leak, pressure test

Just plug the line.

You don't need to pressure test the upper and lower units separately. Just drain the oil, plug the line. Pressurize, and see if it holds pressure. If it's losing pressure, soapy water around seals and other possible leak areas is a good way to find the leaks. (if it bubbles, there's an air leak).

If you can't find the leak that way, separating the upper and lower, and testing that way could be necessary, but it's always easier to just test it all as one unit to start with. Might be something simple...

 

[1coolguy]

Re: Alpha 1 Gen II gear lube leak, pressure test

Thanks for your reply. I actually know that there is a leak because I can see the general area where the oil is leaking from, somewhere between the lower and upper unit. But I can't specifically see exactly where it's coming from without separating the two units. You mention to plug the line. If I do separate the two units, do you know what the best way to plug the oil passage between the two units? I think its about a 3/16th inch diameter hole, but I'm not sure what a good way would be to plug that without causing any damage to the units.