I got the tranny out the other night, was not all that difficult - shaft slid back into stuffing box remarkably easy. I tightened everything back up to prevent water leakage. Our regional Yanmar rep is Mack Boring and have had no luck as of yet in obtaining schematic of tranny which has been promised now over several days. Unfortunately, the closest location to me is a 4+hour drive, so I can't "just go" and get it. Mastry does not cover my area. I think I've located the problem with my existing unit but without a parts catalog I'm dead in the water, both literally and figuratively!
We'll keep on trying though.