Type the number from the transom and the decoder splits it into its parts. It accepts spaces and hyphens, and a two-letter country code in front.
The format
33 CFR 181.25 sets twelve characters with no slashes, hyphens or spaces:
| Characters | Meaning |
|---|---|
| 1 to 3 | Manufacturer identification code (MIC) |
| 4 to 8 | Serial number, letters or digits, never I, O or Q |
| 9 | Month of build or certification, A for January to L for December |
| 10 | Last digit of the year of build or certification |
| 11 and 12 | Model year, last two digits |
Character 10 gives only the last digit of the year, so the decoder takes the year ending in that digit nearest the model year.
Where to find it, and what to check
181.29 puts the primary HIN on the starboard outboard side of the transom, within two inches of the top of the transom, gunwale or hull-deck joint, whichever is lowest. A duplicate goes in a hidden spot inside the boat or under a fitting. The number must be carved, molded, stamped or fixed so that removal or alteration would show, and a separate plate must be fastened so that taking it off would scar the hull. The characters are at least ¼ in high.
Compare the HIN on the transom with the registration or title, the bill of sale and the builder's plate. Signs to note: a plate held by screws or rivets with no scarring around it, filler or fresh gelcoat around the number, characters that don't line up, or a model year that doesn't fit the boat. Write down exactly what you saw and leave the conclusion to the authorities.
European boats
The Recreational Craft Directive asks for a watercraft identification number with the manufacturer's country code, the manufacturer's code, a serial number, the month and year of production and the model year. The detailed layout is set in the harmonised standard. On US boats, 181.27 allows "US-" in front of the HIN.
Citing it in a report
"HIN ABC12345D798, stamped in the starboard transom, matches the title. Manufacturer code ABC, built or certified April 1997, model year 1998. Duplicate HIN not located." Give the number, where it was found, whether it matched the papers and whether the duplicate was found.