Have you had it pressure-tested? You didnt mention the shift-shaft seal which can leak as badly as anything. And there have been gearcases with pinholes in them. You get it hot running down the river, and then when you shut down, it gets buried in cooler water and as the air/oil inside contracts on cooling it can suck in water.First step is to make sure that after replacing the seals, it will hold pressure properly. And you could even try a vacuum test as well as there are cases where a seal will hold +pressure back, but collapse and leak on -pressure.If it is the propshaft, you should be able to see the damage.BTW I have also seen some bearing carriers that were porous, there was a group down in LA that sold racing carriers and they had a bad lot they had to send off to be impregnated with something that stopped this kind of leaking.A pressure test will tell a lot by pinpointing where the leak is occuring, otherwise there are too many places to worry with.2008 Pantera Classic2014 Mercury Pro XS 200
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