I have just pointed out what is the federal law:
Title 33, Code of Federal Regujlations:
§ 181.21 Purpose, applicability and effective dates.
This subpart prescribes the requirements for identification of boats to which section 46 U.S.C. 4301 applies.
[CGD 79–013, 48 FR 40718, Sept. 9, 1983, as amended by USCG–1998–3799, 63 FR 35534, June 30, 1998; USCG–1999–5832, 64 FR 34716, June 29, 1999]
§ 181.23 Hull identification numbers required.
(a) A manufacturer (or importer), as defined in §181.3 of this part, must identify each boat produced or imported with two hull identification numbers that meet the requirements of this subpart:
(1) A primary hull identification number affixed in accordance with §§181.29(a) and (c) of this subpart; and
(2) A duplicate hull identification number affixed in accordance with §§181.29(b) and (c) of this subpart.
(b) A person who builds or imports a boat for his or her own use and not for the purposes of sale, must identify that boat with two hull identification numbers that meet the requirements of this subpart.
(c) No person may assign the same hull identification number to more than one boat.
§ 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.
§ 181.27 Information displayed near hull identification number.
With the exception of the characters “US-”, which constitute the country of origin code for the United States, if information is displayed on the boat within 2 inches of the 12-character hull identification number (HIN), that information must be separated from the HIN by means of borders or must be on a separate label, so that it will not be interpreted as part of the hull identification number.
[USCG–2003–14272, 69 FR 33860, June 17, 2004]
§ 181.29 Hull identification number display.
Two identical hull identification numbers are required to be displayed on each boat hull..... etc
For the most part folks who work at the DMV or tag offices know little about boat registrations, and would not know the difference between a 12 and 13 digit HIN. Now if you came in with a 18 digit VIN, then there would be some eyebrows raised! I don't foresee any problem with the CG--except if someone were to document the vessel, or question the HIN. Just seems like a very strange practice to producing a product contrary to what is indicated in Federal Law, and the knowledge that the 13 digit (or more) HIN has been raised as recently as last year and rejected by the CG.
Most folks don't even look at the HIN when they buy a boat. A good marine surveyor will either photograph or make a pencil rubbing of the HIN as part of his report.