Part of the Inventory
I would also opine that the unobserved hull damage (hope it was a good repair job and that the structural integrety is sound) and the sail are two separate items.Is the sail fitted for the boat you bought? Is it in good condition that might have helped you decide to make the boat purchase since you knew that you probably wouldn't need new sails for quite a few years? Was the sail on board the boat, or shown to you, when you made your pre-purchase inspection? If these, or any one of many more situations apply, and unless the sail was specifically excluded from the purchase, there would be nothing unethical about standing firm that the sail is in the category of normal inventory of boat items that are transferred from buyer to seller. A portion of the agreed price is the value of the sail. Very often boats are sold with several sails included. They're part of the purchase. Same with spare parts for the engine that the owner may have purchased but never used but were left on the boat. Or the new winches that a seller might have installed a couple of years ago. Or an old replaced halyard that was left on board that you now can use for a clothesline in your back yard. Or the fire extinguisher. He can't claim any of these back. Anything that is consistent with the normal equipment of a boat that is not excluded in the agreement are now yours. (I would say the same would apply to personal property that a seller just found it easier to leave on board. Cleaning supplies. Nautical charts. An old rusty tool kit. Life vests. But if the boat was cleared of obvious personal property and you later found on board (say) the seller's clarinet that he overlooked, then that should be returned, no strings attached.) I'm curious, why does the seller want the sail back? If (say) the sail doesn't fit on your 24' boat, but instead is a 130% Genoa that fits on the seller's (say) 46' cruiser, its likely that the seller did not intend the sail to be part of your transaction. But as above, if you had placed value on the sail (as you expected it to fit on your boat) then you would be within your rights to insist that the seller make a reasonable refund to you for the return. If the seller wants the sail back to sell it on eBay, you'll probably have your own appropriate response to him.