1625-0056 Stat/Authority

33 CFR 181.25 (up to date as of 12/10/2025)
Hull identification number format.

33 CFR 181.25 (Dec. 10, 2025)

This content is from the eCFR and is authoritative but unofficial.

Title 33 —Navigation and Navigable Waters
Chapter I —Coast Guard, Department of Homeland Security
Subchapter S —Boating Safety
Part 181 —Manufacturer Requirements
Subpart C —Identification of Boats
Source: CGD 79-013, 48 FR 40718, Sept. 9, 1983, unless otherwise noted.
Authority: 46 U.S.C. 4302; DHS Delegation 00170.1, Revision No. 01.4.
Source: CGD 72-60, 37 FR 15779, Aug. 4, 1972, unless otherwise noted.

§ 181.25 Hull identification number format.
Each of the hull identification numbers required by § 181.23 must consist of twelve characters, uninterrupted by
slashes, hyphens, or spaces, as follows:
(a) The first three characters must be a manufacturer identification code assigned under § 181.31(a) or the
importer designation assigned under § 181.31(b).
(b) Characters four through eight must be a serial number assigned by the manufacturer in letters of the
English alphabet, or Arabic numerals, or both, except the letters I, O, and Q.
(c) Characters nine and ten must indicate the month and year of certification when a date of certification is
required. In all other cases characters nine and ten must indicate the date of manufacture. The date
indicated can be no earlier than the date construction or assembly began and no later than the date the
boat leaves the place of manufacture or assembly or is imported into the United States for the purposes
of sale. Character nine must be indicated using letters of the English alphabet. The first month of the year,
January, must be designated by the letter “A”, the second month, February, by the letter “B”, and so on until
the last month of the year, December. Character ten must be the last digit of the year of manufacture or
certification and must be an Arabic numeral.
(d) Characters eleven and twelve must indicate the model year using Arabic numerals for the last two
numbers of the model year such as “82” for 1982 and “83” for 1983.

33 CFR 181.25(d) (enhanced display)

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