The HIN must be permanently marked on the helm of the boat leading to the port. If the vessel is driven by an outboard engine, it must be indicated separately with its serial number. In some states, it may not be necessary to sell boats to close the sale, but using a sale is a good idea because it proves the details of the deal. If the boat has a title – required in most states for boats longer than 16 feet – that title still has to be transferred from the seller to the buyer in accordance with state regulations. The use of a formal boat purchase contract protects both the buyer and the seller and contributes significantly to avoiding any misunderstanding between the parties.