Thanks kaptain Jack I would agree with you in your situation and get the sub back to sea but I just wanted to point out that it would be a good idea to check if there is a support bushing in that motor mount ,it must be a bushung that supports the shaft not just a seal seat,if not the seal will fail again .
You could install a bushing of the right size and press it in,try Smallparts.com for there extensize selection of bushings and I think they even have simitar seals.

Good Luck Dave!