I was going to say this same thing. It is nice to not pay property tax etc. on the boat. Interesting to hear the different things that states require, and the extra taxes they collect, just because someone bought something, that taxes had been paid for the other time that the same thing was purchased.
when i buy/sell I usually get a bill of sale, title, and keep a copy of form of payment when applicable. some cash deals are just that and as is.