Leaking Prop Shaft Seal 1963 75hp

[yorab]

Motor in signature. I'm very disappointed. I was looking for a used gearcase head (prop shaft bearing carrier) because one of the four ribs that keep out fishing line had broken off. I had a new seal and bearing so I just wanted the head itself. However, I couldn't find a used one so I had to buy a new head that included the bearing and seal that I already have. I just tested it and found that the seal leaks around the OD. I'm thinking that I have no options except to replace the seal. Am I right? Can I try to seat it in a bit deeper? Anything else I can do besides buying another seal or head?

I'm also thinking that I'll have to pull the gearcase head completely off to replace the seal. If so, then I'll probably need to replace those o-rings that go under the head of the gearcase head screws. Is this right?