Boat HIN decoder
Paste a 12-character Hull Identification Number. This reads the structure the Coast Guard defined, tells you when the hull was actually built, and flags the mismatches that cause title problems.
What the twelve characters mean
| Position | Meaning |
|---|---|
| 1–3 | Manufacturer Identification Code (MIC), assigned by the Coast Guard. Three characters, and it is the only part that identifies the builder. |
| 4–8 | Hull serial number, the builder's own sequence. Format is entirely up to the builder, so a low number does not prove an early hull. |
| 9 | Month of certification, as a letter. A = January through L = December. |
| 10 | Last digit of the year of certification, so it repeats every decade. Context (the model year that follows) resolves which decade. |
| 11–12 | Model year. This is what a listing calls "the year", and it is routinely one year ahead of the build date. |
Hulls built before August 1984 used two earlier date formats, and which one a builder used was not consistently recorded. This tool will not guess a build date for those: it reads the MIC and serial, marks the date as unreliable, and tells you to confirm with the builder or an owners' association. That is also true of any hull re-stamped with a replacement HIN.
Before November 1, 1972 there was no HIN requirement at all. A boat of that vintage with a HIN either got one later or has one applied by a state.
The three HIN checks that actually protect you
- Transom HIN versus the paperwork. Photograph the transom HIN and read it against the title, the registration and the bill of sale, character by character. A single transposed character is enough to stall a title transfer for months.
- Find the second HIN. Since 1972 builders have been required to apply a duplicate HIN in an unexposed location, and they were not told to tell you where. Common spots are inside a cockpit locker, under a hatch lip, beneath the mast step, or inside the transom. If the hidden one and the transom one disagree, stop.
- Run it for a hull history. The HIN is how you check documented ownership, recorded liens, and reported accidents or salvage. A clean survey on a hull with a salvage history is still a boat you should think hard about.
The pre-purchase inspection kit for your boat
A decoded HIN tells you what the boat is. The kit tells you what is wrong with it: the documented weak points for your exact model, the cost of each one, and the findings that should end the deal.
See the inspection kits