What Is a HIN Number? Hull Identification Number Explained

If you are buying, selling, or insuring a boat in the United States, you need to know the HIN. The Hull Identification Number is a 12-character code that identifies every recreational vessel built or imported since 1972. It is the closest thing the boating world has to a car's VIN, and it is the starting point for every background check you run on a boat.

What a HIN Looks Like

A standard HIN is 12 characters long, with no spaces or dashes. It contains a mix of letters and numbers. Here is an example:

Let's break that down:

• SER (characters 1 through 3): Manufacturer Identification Code (MIC). This three-letter code is assigned by the U.S. Coast Guard and identifies the builder. In this example, “SER” is Sea Ray.
• 12345 (characters 4 through 8): Hull serial number. Unique to this specific boat from this manufacturer. Can be letters or numbers.
• L506 (characters 9 through 12): Date code. “L” = December (A=January through L=December), “5” = last digit of production year (2005), “06” = model year (2006).

Where to Find the HIN on a Boat

Federal law (33 CFR 181) requires two HIN locations on every boat:

Primary location (visible)

The main HIN must be on the starboard (right) side of the transom. It should be within two inches of the top of the hull sides or the gunwale, and within two inches of the transom or stern. On boats without a transom (like pontoons, PWCs, or inflatables), look on the starboard outboard side of the hull, aft.

The HIN can be stamped directly into the fiberglass, molded into the hull, engraved on a plate, or attached via a riveted tag. It should be clearly legible.

Secondary location (hidden)

A duplicate HIN is required in a hidden location somewhere inside the boat. The exact spot varies by manufacturer. Common locations include under a deck plate, beneath the engine cover, inside a storage compartment, or behind an access panel. The purpose is to provide a check against tampering with the primary HIN.

How to Decode a HIN

There are two date formats, depending on when the boat was built.

Current format (August 1984 to present)

Characters 9 through 12 encode the production date:

• Character 9: Month of production (A=January, B=February ... L=December)
• Character 10: Last digit of production year
• Characters 11 and 12: Model year (two digits)

Example: L506 means production month December, production year ending in 5 (2005), model year 2006.

Straight-year format (November 1972 through July 1984)

Older boats use a simpler date code. Characters 9 through 12 are just the month and year of certification, formatted as MMYY. For example, 0880 means August 1980.

The MIC: Identifying the manufacturer

The first three characters are the Manufacturer Identification Code. The USCG maintains a registry of over 16,000 MIC codes, covering active and inactive builders. You can search MIC codes on our free HIN check tool, which decodes the full HIN and identifies the manufacturer, production date, and model year.

Why the HIN Matters When Buying a Used Boat

The HIN is the key that unlocks every background check:

• Stolen vessel check: Law enforcement databases index stolen boats by HIN. No HIN, no search.
• Lien search: Maritime lien records and USCG documentation are tied to the HIN.
• Recall lookup: The MIC portion identifies the manufacturer, which links to USCG recall notices.
• Title verification: State titling agencies and the USCG National Vessel Documentation Center track boats by HIN.
• Insurance: Your insurer will verify the HIN against claims databases. A flagged HIN can make a boat uninsurable.

Common HIN Questions

Do all boats have a HIN?

All boats manufactured or imported for sale in the U.S. after November 1, 1972 are required to have a HIN. Boats built before that date, homemade boats, and some foreign vessels may not have one. States typically assign a “state-issued HIN” to boats that enter the system without one.

Can a HIN be changed or faked?

Altering, removing, or counterfeiting a HIN is a federal offense under 18 USC 511. It does happen, usually in connection with stolen vessels. That is why the hidden secondary HIN exists: if someone re-stamps the transom HIN, the hidden one should still show the original.

Is a HIN the same as a boat registration number?

No. The HIN is permanently assigned by the manufacturer and never changes. A registration number (like FL 1234 AB) is assigned by the state and changes when the boat is sold to a new owner or registered in a different state. The HIN stays with the hull for life.