All boats manufactured or imported on or after November 1, 1972, must bear a HIN, and this HIN must be identified during boat registration. Vessels manufactured or imported before 1972 are EXEMPT because they often do not have a HIN.
If your vessel is homemade, you must apply either with your State Department of Motor Vehicles, or directly with the Coast Guard for Documentation. On homemade vessels, there are circumstances where each state and the U.S. Coast Guard will assign hull numbers directly to an applicant. State issued hull numbers will begin with their standard registration prefix followed by the letter “Z”. Coast Guard issued hull identification numbers are prefixed by “USZ”.
The Hull Identification Number (HIN) is a 12- or 14-character serial number that uniquely identifies a boat. The HIN is analogous to a VIN on a car.
The HIN is found on a metal or plastic plate, typically on the transom of the boat, usually on the right starboard (right) side of the transom within two inches of the top of transom, gunwale, or hull/deck joint, whichever is lowest.
On vessels without transoms, or impractical to use transoms, the HIN is usually affixed to the starboard (right) outboard side of hull, aft, within one foot of the stern and within two inches of the top of the hull side, gunwale or hull/deck joint, whichever is lowest.
On catamarans and pontoon boats with replaceable hulls, the HIN is usually affixed to the aft crossbeam, within one foot of the starboard (right) hull attachment.
On US Coast Guard Documented Vessels, the Hull Identification Number is displayed on the top of the CG-1270 Certificate of Documentation next to the Vessel Official Number
The Code of Federal Regulations CFR Title 46 Part 67 regulates Hull Identification Numbers as such:
§ 181.23 Hull identification numbers required.
(a) A manufacturer must identify each boat produced or imported with primary and secondary hull identification numbers permanently affixed in accordance with § 181.29 of this subpart.
(b) A person who manufactures or imports a boat for his or her own use and not for sale must obtain the required hull identification number in accordance with the requirements of the issuing authority listed in 33 CFR part 173, Appendix A for the boat‘s State of principal operation and permanently affix the HIN to the boat in accordance with § 181.29 of this subpart.
(c) No person may assign the same HIN to more than one boat.
§ 181.29 Hull identification number display.
Two identical hull identification numbers are required to be displayed on each boat hull.
(a) The primary hull identification number must be affixed –
(1) On boats with transoms, to the starboard outboard side of the transom within two inches of the top of the transom, gunwale, or hull/deck joint, whichever is lowest.
(2) On boats without transoms or on boats on which it would be impractical to use the transom, to the starboard outboard side of the hull, aft, within one foot of the stern and within two inches of the top of the hull side, gunwale or hull/deck joint, whichever is lowest.
(3) On catamarans and pontoon boats which have readily replaceable hulls, to the aft crossbeam within one foot of the starboard hull attachment.
(4) If the hull identification number would not be visible, because of rails, fittings, or other accessories, the number must be affixed as near as possible to the location specified in paragraph (a) of this section.
(b) The duplicate hull identification number must be affixed in an unexposed location on the interior of the boat or beneath a fitting or item of hardware.
(c) Each hull identification number must be carved, burned, stamped, embossed, molded, bonded, or otherwise permanently affixed to the boat so that alteration, removal, or replacement would be obvious. If the number is on a separate plate, the plate must be fastened in such a manner that its removal would normally cause some scarring of or damage to the surrounding hull area. A hull identification number must not be attached to parts of the boat that are removable.
(d) The characters of each hull identification number must be no less than one-fourth of an inch high.
