Something isn't quite adding up with the salesman's story which is to be expected. I'll just add that at least in my state, there is no sales tax payable on used boats from private parties or from brokerage transactions. There is sales tax payable from used boats bought from dealers however. Sales tax is only payable on the value of the trailer on the sale of a boat. Our sales tax is up to 7.875% so I only buy used boats from private parties since it is a meaningful amount of money on a bigger transaction.