The process doesn't really change. The buyer hands over the
money, the seller hands over the
boat and the title. The buyer may also have to fill out some paperwork declaring/proving that the boat is in a different state, so they don't owe any sales tax in the seller's state, if that is applicable.
One caveat is that it is becoming a common scam to send a cashiers check (or paypal payment) and a third party to pick up the boat. When I bought a boat unseen, I hired a
surveyor to go buy and confirm that the boat seemed in like new condition (it was a dealer's
boat show model), wired them the
money, and arranged to have a shipper bring it to me. Now that I am selling the same boat, I am not sure I that would accept a similar arrangement, because so many scammers have already contacted me.