Federal regulations in the US and the Recreational Craft Directive in the EU both require two HINs per boat: one on the outside, one hidden inside. Finding both — and confirming they match — is essential before buying a used boat, registering with your state DMV or maritime authority, or filing an insurance claim.
If your boat is post-1972 (US) or post-1998 (EU), both numbers must be there. Below is where to look on every common hull type.
The exterior HIN: transom, starboard side, near the top
Stand at the back of the boat. Look at the right-hand side (starboard) of the transom, as close to the top edge as possible. The HIN should be stamped, engraved, or molded into the hull material at least 6 millimeters (about ¼ inch) tall. On most modern boats it's about 8–12 mm.
What it looks like:
- Fiberglass boats: raised lettering molded directly into the gelcoat, or a small metal plaque riveted on
- Aluminum hulls: stamped into the metal with a depth gauge
- Wood or cold-molded: usually on a metal plaque since wood doesn't hold stamping well
- Inflatables and RIBs: on the rigid transom (RIB) or on a sewn-in plate near the transom (pure inflatable)
Pro tip: If the HIN is faint, take a sheet of plain paper and a soft pencil. Hold the paper against the transom and rub the side of the pencil over the area — the raised or recessed lettering shows through. This works for nearly any stamped HIN even when it's been painted over.
The interior (hidden) HIN: builder's choice
The interior HIN is a duplicate of the exterior one, hidden somewhere a thief is unlikely to find but a maritime surveyor can. The manufacturer reports the hidden location to the USCG/EU authority but doesn't disclose it publicly.
For each type of boat, here are the most common hiding spots based on industry experience:
Sailboats (under 12 m / 40 ft)
- Beneath the navigation table or chart-table flooring
- Inside the engine compartment, stamped on a stringer
- Behind the companionway steps
- Under the V-berth, on the hull side near the bow
- Inside the anchor locker, low on the bulkhead
Powerboats and cruisers
- Inside the engine compartment on a stringer or transom interior
- Under the helm console (lift the panel or seat cushion)
- Inside a cockpit locker, low on the hull
- Below the gunwale on the starboard side
- Under the lower seat cushions in the cabin (smaller cruisers)
Personal watercraft (jet skis)
- Inside the engine compartment (lift the seat)
- On the inside of the hull near the bow, requires bow access
- Often a small metal label rather than stamping
Pontoon boats
- Stamped into the starboard pontoon, inside, near the rear cross-member
- On the underside of the deck near the rear-starboard corner
- Inside the rear locker
Inflatables / RIBs
- RIBs: on the rigid hull interior, usually under the seating
- Pure inflatables: on a label sewn into the seam, often near the transom
Both HINs must match
Once you find both, compare them character by character. They must be identical. Common mismatches and what they mean:
- One character off: usually a manufacturer typo at the factory. Annoying but typically harmless. Document it.
- Multiple characters differ: serious. The hull may have been repaired by replacing a section, swapped onto another boat's deck/cabin, or had the HIN deliberately altered. Stop the purchase and consult a marine surveyor or maritime authority.
- One HIN missing entirely: illegal in both US and EU. The boat cannot be legally sold or registered until a replacement is officially issued by the authority.
- Both HINs missing: walk away. The boat may be stolen, salvaged, or built before HIN requirements.
If you can't find the hidden HIN
Some hiding spots are devilish. If you've searched thoroughly and can't find it, options are:
- Contact the manufacturer with the visible HIN — they often have records of where they put the hidden one for that hull
- Hire a marine surveyor — they know the common spots brand by brand
- For US boats, the USCG MIC database (we've integrated all 16,000+ entries on this site) may list builder contact info
Once you've found it: decode it
Use our free HIN decoder to instantly see what your HIN tells you: manufacturer name, country, production month and year, model year, and any formatting issues. The decoder handles both US (12-char) and EU/CE (14-char) formats automatically.
Frequently asked questions
What if there's no HIN visible on the transom?
Common causes: faded paint over the HIN, sun damage to the gelcoat, a vinyl wrap covering it, or hull repair that ground the stamping smooth. Try lighting it from a low angle (early morning or late afternoon sun) — stamped HINs cast shadows that reveal them. If still not visible, the hidden secondary HIN inside the boat is your fallback. If neither exists or they don't match, contact your national authority before purchase or registration.
Where exactly is the hidden HIN?
The manufacturer chooses the hidden location, but common spots include: under the helm console (lift the cushion or panel), inside the engine compartment on a stringer, beneath a deck plate near the bow, inside an anchor locker, under the seating in a cockpit locker. Surveyors typically know the favorite hiding spots for each major brand.
Should the two HINs match?
Yes, exactly — same 12 or 14 characters, no exceptions. If they differ, the boat may have been re-titled, salvaged, repaired with a different hull section, or had its HIN tampered with. Walk away from the deal until the discrepancy is officially resolved.
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- Decode boat year from HINProduction year vs model year, the 1-digit ambiguity, and how to tell a 1984 from a 2014