I would consult the boating
industry association (bia) asap.
Generally you can't but you would need to read the terms very carefully. If the contract is considered unfair your lawyer might be able to get the contract set aside?..
Alternatively, talk to the dealer, ask them to on sell your boat as ordered asap to the next purchaser, you will need to pay his commission but that might be a small cost.
With the new new boat you could also tell them the situation and tell them they have to on sell the old new boat as a condition of buying
a new new boat.
Remember the waterfront is a small community, best not to make enemies!