I assume that means you paid cash and didn't take a loan. When I bought my boat, the previous owner had lost the title. We looked at several different ways we could do the exchange with the money while waiting on the title, but in the end we just waited. We decided it would be smarter, and also the bank would not fund the loan without seeing the title.
Looking back, it was the smart thing to do. I think if I were buying another and I was paying cash, it wouldn't happen until I saw the title.
By the way, in the state of New York, it takes 12 weeks to get a replacement boat title. Whatever state your seller is in may have a similar policy.