There are some variables, even in a cash sale
Will your insurance
company require a survey
? Most do.
Do you want to document your boat? There are fees
to do that.
You mentioned state registration
, some brokers will do that and charge a fee to complete the paperwork. In NY a broker has to collect the sales tax, so there is no cheating and sales tax must be paid at the time the boat is registered.
Depending on the particular sale
there may be charges for sending documents by overnight mail, if the current
owner is out of state.
There may be fees
to pay off an existing loan.
Your best bet is to ask your broker about the extra expenses.