How to Read a Boat Hull Identification Number (HIN)

A Hull Identification Number (HIN) is the maritime equivalent of a car's VIN. Stamped permanently onto the transom of every recreational boat built since November 1, 1972, this 12-character code provides critical legal documentation of who built the boat, when it left the assembly facility, and what model year it represents.

The Anatomy of a Modern 12-Character HIN

Every recreational boat constructed since August 1, 1984, complies with the federal standard defined in Title 33 of the Code of Federal Regulations (33 CFR Part 181). The code is organized into four standardized blocks:

1. Manufacturer Identification Code (Characters 1–3)

The first three letters represent the Manufacturer Identification Code (MIC), granted exclusively by the US Coast Guard Boating Safety Division. This code links directly to the registered legal entity that built or commercially imported the hull. For example:

• SER: Sea Ray Boats
• BWC: Boston Whaler
• BUJ: Tracker Marine Group (White River Marine)
• FGJ: Chaparral Boats
• LUN: Lund Boat Company

If the first three letters are a state postal abbreviation followed by the letter Z (such as FLZ or TXZ), the hull was issued by a state department of motor vehicles or wildlife commission for a homemade or rebuilt vessel.

2. Hull Serial Number (Characters 4–8)

Characters 4 through 8 represent the unique serial sequence assigned by the manufacturer. Boat builders may use numbers, letters, or a combination of both. However, federal regulation strictly bans the letters I, O, and Q in characters 4 through 12 to eliminate confusion with numbers one and zero.

3. Month and Year of Production (Characters 9–10)

Character 9 indicates the month the boat was certified and built:

Character 10 represents the last digit of the calendar production year. In our example D4, the letter D means April, and the digit 4 represents the year 2024.

4. Model Year (Characters 11–12)

Characters 11 and 12 designate the official model year certified by the manufacturer. For example, 24 represents the 2024 model year. Many boat manufacturers launch new model years in August or September of the prior calendar year. In such cases, a boat built in September 2023 will carry I324 (September 2023 production, 2024 model year).