A boat bill of sale (also called a boat purchase agreement) is a document used to detail the terms of a transaction between a private seller and buyer. The form details information about the buyer, the seller, and the vessel and is required to be included in a registration application to the state.A Michigan boat bill of sale records a transaction involving the purchase of a motorboat, sailboat, canoe, or other vessel. The Michigan boat bill of sale form is a document that reports the key elements regarding the sale of a boat for a sum of money. Owner states that this boat is sold free and clear of any liens, bills or encumbrances of any nature except as stated below. A Michigan boat bill of sale is a document proving that selling or buying a watercraft has taken place in the state.