The transmission on left (starb.) side engine keeps building pressure and blowing the main seal. My mechanic seems to think I need to replace it, which I feel he is probably correct. He mentioned buying one used, but there seems to be some places that can rebuild or sell a rebuilt at a reasonable cost. The trans. is mated to a TRS outdrive............Any thoughts as to my best course of action? Thanks

there is one TRS velvet drive on ebay for 500 or make offer. says used-worked when removed. the are a zillion velvet drives on ebay 250 to 2500. but I don't think they can be used on a TRS setup. check craigslist in your area too. I think the TRS tailstock is integral to trans case. but you could use most internal parts except tailshaft-I think. blowing seal, it may just be a check valve in front pump that is stuck or something simple like that. I know it is the simplest automatic transmission ever made. it makes no diff if port or starboard. same rotation in a trs setup. even an opposite rotation velvet drive can be flipped by turning a plate around in front pump. where are you. there are a lot of TRS guys on this site. but you can't enlist help from somebody over a hundred miles or so away.

resqme,left is port,a velvet drive can be totally rebuilt,it is a pretty simple job for any trans guy.i would rebuild instead of bying a used one that may have more problems than yours.

Is your mechanic using the rubber seal that comes in the alto kit? If so that's your problem. The rubber seals only stay in sometimes with loctite.

The problem with the early transmissions is the Velvet.. it doesn`t hold up very well in a wet environment but it is beautiful... later they switched to a metal case and most of those issues were eliminated.

http://www.youtube.com/watch?v=w-eb61BLIWw

I've bought genuine bw parts from here http://www.marinegears.com/ They also will rebuild yours

Yes. My buddy who rebuilds marine transmissions had that issue.

Also, I believe if the front pump is worn, you may get pressure blowing against the seal.

Yes a worn pump will do that, actually a new pump will sometimes do it.

We use a hi-temp superglue on our seals. And more importantly we also figured out a mod to the pump to relieve the pressure. The newest pumps direct from Velvet Drive are machined with a lip to retain the seal but they didn't do anything to relieve the pressure. So some of them will build up so much pressure that the seal gets a hemorrhoid.

Check runout (tir) between the crankshaft and the flywheel housing bore. High runout (over .007" if I remember right) can cause issues with the front needle bearing and the pump.

Yes, that too - good catch
Also need to check the runout on the drive plate.

The truth is no one checks this stuff. We have it in our instructions but I doubt if anyone reads them.