All boats manufactured or imported after 1984 are required to have hull identification numbers in two places, with one being clearly visible from the outside of the boat on the starboard side of the transom and within two inches of the top of the hull, deck joint, gunwale or transom, whichever is lowest. Boats without a transom, sailboats, pontoon boats and catamarans have varying location requirements for HIN positioning on the stern of the boat.
A boat without a transom or with no practical location on the transom must have its HIN mounted on the outside of the hull on the starboard side within one foot of the stern and two inches of the top of the lowest point of either the hull, deck joint or gunwale. Pontoon boats and catamarans require that the HIN must be attached to the crossbeam, within one foot of the starboard hull attachment.
The second HIN number is to be placed somewhere inside of the boat in a hidden location under a fitting or other hardware item. This is to help identify stolen boats. The HIN number is the marine manufacturer's version of the automakers VIN system.
One HIN is required on all boats manufactured or imported after 1972 but before 1984, and it is typically affixed to the upper right outside corner of the transom.