Many dealers are not set up to take in boat trades because they do not have the means to service, move or inspect them. However, plenty of other dealers will do what they can to make a car deal, even if it includes taking in a boat. The process may differ by dealer, but trading your boat can be a possibility.
You can visit dealership websites, but unless you see "we accept anything for trade," or something similar, you probably will have to call around to find a dealer to work with you. When you call, ask to speak to a sales manager; taking a boat for trade is not a salesperson's decision. Before calling, you should have an idea of what kind of car you want. Most dealerships showcase their used and new car inventories online.
Once you find a dealership that will accept a boat for trade, arrange to have it appraised. A dealership may want only relevant boat information (year, make and level) before having you bring it in for appraisal. Don't be surprised if this process takes several days. The dealer will call various wholesalers and connections she has to try and gauge a value and whether or not she can sell the boat to another business or person. Once she has an interested buyer, she may arrange for you to bring the boat in.
Once you do find a dealer to take your boat, the paperwork required to trade the boat in is very similar to car paperwork. You will need the boat's title and any applicable loan information, such as a lien release if the loan has been satisfied or your bank information and account number if not. The dealer will call to obtain your boat's payoff amount and arrange to pay off the boat to complete the trade process. Be sure to have your information handy before contacting dealers.
Because finding a dealership to accept your boat trade may prove a bit of a challenge, you may want to sell the boat on your own before pursuing a vehicle purchase. This way, you can probably get more money for the sale, which you can use toward your car purchase. You can advertise your boat for sale in local classifieds or call a boat dealer to find out if you can sell it on consignment, which means the dealer will sell your boat at retail and keep a percentage of the profit.