Free Boat HIN Decoder - Read Your Hull Number
A hull identification number is the 12-character code the builder stamped into your transom. Paste it below and we will read the manufacturer, serial, build date and model year out of it.
How a HIN is put together
Since August 1984 every hull sold in the US carries a 12-character HIN in a fixed format:
| Position | What it is | Example |
|---|---|---|
| 1–3 | Manufacturer Identification Code (MIC), assigned by the US Coast Guard | BUJ = Bayliner |
| 4–8 | Hull serial number, the builder’s own sequence | 12345 |
| 9–10 | Month and year of build — A=January through L=December, then the year digit | A4 = January, year ending 4 |
| 11–12 | Model year | 04 = 2004 |
A HIN is not your registration number
People mix these up constantly, so plainly:
- The HIN is permanent, assigned by the builder, stamped into the hull, and never displayed in large letters. It is the boat’s VIN.
- The registration number is issued by your state, changes if you move or re-register, and is the one you must display in 3-inch block characters on both sides of the bow.
If you came here because you need the second one made, that is what we do — $19 a pair.
If the HIN is missing or unreadable
Pre-1972 hulls may genuinely never have had one. From 1972 onward it should be there, and a hull with a ground-off or illegible HIN is a serious red flag on a used purchase — it is how stolen boats get laundered. Your state agency can issue a replacement HIN for a legitimately unmarked hull, but you will need to prove ownership.
Check the starboard transom first, then inside a locker or under the gunwale on the starboard side — builders are required to put a duplicate in an unexposed location.
Questions people actually ask
How do I find the hull number on my boat?
Starboard side of the transom, within a couple of inches of the top edge. There is also a duplicate hidden somewhere unexposed - inside a locker, under the gunwale, or beneath a deck plate on the starboard side.
Can you tell the year of a boat by the hull number?
Yes. The last two characters are the model year, and characters 9-10 give the month and year it was actually built. The two can differ - a boat built in September 2003 is commonly a 2004 model.
Is the hull number the same as the VIN?
It is the same idea - a permanent, unique builder-assigned identifier - but boats use a 12-character HIN rather than a 17-character VIN, and the formats are different. Boat trailers have their own separate VIN.
What happens if my boat has no Hull Identification Number?
Hulls built before 1972 may never have had one. After that it is required, and a missing or altered HIN is a major warning sign on a used boat. Your state agency can assign a replacement HIN if you can document ownership.
Can I look up who owns a boat from the HIN?
Not publicly, in most states - ownership records are restricted. A HIN will tell you the builder, serial and age, and USCG documented vessels are searchable in the federal vessel database, but state registration owner data generally is not open.