I would say that you would indeed be owed the money left over.  The bank has no legal right to keep the money that is received over and above the loan amount remaining on the boat.  If there were a deficiency on the sale - that they got less than you owed - you can guarantee that they would be coming after you for the money.  So I think that you need to go after them.  Contact them in writing and ask fr an accounting of the sale.  Once you receive it then you will know how to proceed.  Be aware that you may indeed have additional legal fees, etc.,  associated with the repossess and the sale to decrease the overage amount.  Good luck.