A HIN — Hull Identification Number — is the 12-character serial number that uniquely identifies one boat hull. It is the marine equivalent of a car's VIN. Every boat built or imported for sale in the United States since 1 November 1972 is required by federal law to have one, and no two hulls share the same number.
The HIN is what makes a boat traceable. It ties a physical hull to its build date, its manufacturer, its title and registration history, any accident or theft record filed against it, and any safety recall the Coast Guard has issued for that model.
The requirement comes from the Federal Boat Safety Act of 1971, implemented in 33 CFR Part 181. Congress wanted two things: a reliable way to reach owners when a defect is found, and a way to make stolen hulls harder to launder. The HIN does both. When a manufacturer issues a recall, the Coast Guard publishes it against a range of hull numbers — without a HIN, there is no way to tell whether a specific boat is inside that range.
| From the HIN alone | Only from a history report |
|---|---|
| Who built the hull | Past registered owners |
| Month and year of manufacture | Reported accidents or salvage |
| Model year | Theft records |
| Whether the builder is still trading | Outstanding liens |
| Recalls filed against that manufacturer | Title-branding history |
The first column is free and instant — that is what our decoder reads straight out of the Coast Guard's own manufacturer database. The second column requires cross-referencing state title and insurance records, which is what a paid history report buys you.
People search for all three and usually mean the HIN. Strictly: a VIN belongs to a road vehicle, a HIN belongs to a boat hull, and a serial number is the middle five characters of the HIN. A trailer sold with a boat has its own separate VIN, and an outboard engine has its own serial number again — three different numbers on one purchase, so check which one a seller is quoting you.
If a HIN will not decode, the usual explanations are mundane: a transcription error (0 and O, 1 and I, 5 and S are the common ones), a hull built before November 1972 when the format was not yet standardised, or a boat built outside the US for a non-US market. But a HIN that is the wrong length, has been ground down, or does not match the second hidden HIN elsewhere on the hull is a genuine warning sign, and worth walking away from.
Type the 12 characters from your transom and get the model year, build date, manufacturer on record and open recall status — free, no account needed.
Run a free HIN checkHow to read a boat HIN breaks the 12 characters down one by one. Where is the HIN on a boat covers the two places it is legally required to be. And if you already know the builder, go straight to the brand pages for Sea Ray, Bayliner or Boston Whaler.