Look up Hull Identification Numbers on websites such as Boat-History-Report.com, NationalMarineRegister.com and BoatHistoryReport.com. There are also applications available, such as HIN Search Plus, which can be downloaded from the Apple store.
The Hull Identification Number is a 12- or 14-character number to distinguish boats, generally for law enforcement purposes. It is the equivalent of a Vehicle Identification Number on a car.
HIN numbers are required to register any boat that was either manufactured or imported after November 1, 1972. Vessels that were manufactured or imported prior to this date are grandfathered in.
A boat's Hull Identification Number usually appears on the metal or plastic plate on the transom of the boat, typically on the right side within 2 inches of the top. On vessels without transoms, the HIN is usually affixed on starboard outboard side of the hull. On catamarans, pontoon boats and other vessels that have hulls changed more frequently, the HIN is usually on the aft crossbeam, within 1 foot of the starboard hull attachment.
The current HIN version, as of 2015, has been in use since August 1, 1984. The 12-character number includes a three-digit manufacturer code, a five-digit hull serial number and a four-digit date of certification. The manufacturer code consists of letters, the serial number is in numerical figures and the date of certification features only numbers or a combination of letters and numbers.
The version that was used prior to August 1984 had the same first two elements, but the final set of four digits identified the date of certification and the model year with two digits each.