A boat VIN is referred to as a HIN, or Hull Identification Number, and is researched by using websites like Hinvalid.com. Found on the upper starboard transom, or upper right back, the HIN is entered in the search field and used to find vessel registration history and other information.
All boats built or imported since November of 1972 must have a HIN. That includes homemade boats that aren't intended for resale. Builders must go to their state boating agency for the 12-character number. Instead of a manufacturer's identification code, the homemade boat gets the state abbreviation and the letter "Z."
Like a car VIN, the entire HIN can be decoded. As an example, using ABC 12345 1173, the first three letters are the manufacturer's code. This is where the substituted state code and the "Z" are found. The next five numbers are the hull or serial number. The last four numbers indicate the month and model year, in this case November of 1973.
The format for the month and model year does vary among the manufacturers and may have both letters and numbers. Boats built after 1984 use the format ABC 12345 D8 88. The "D8" stands for April and the last digit of the manufacturing year, and the "88" is the model year. A newer boat may have a 15-digit HIN.