The numbers on the side of a boat are usually its state registration numbers, the bold block characters painted near the bow that show the boat is legally registered. But those aren’t the only markings worth knowing. Most boats also carry a 12-character Hull Identification Number on the transom, and smaller boats have a capacity plate near the helm. Larger federally documented vessels skip bow numbers entirely and display a name and hailing port on the hull instead. Each marking does a different job.
State Registration Numbers on the Bow
Those big letters and numbers near the front of a boat are its state registration numbers. Every motorized boat on public waters needs them, with a narrow set of exceptions for federally documented vessels, military craft, and ships’ lifeboats.1eCFR. 33 CFR Part 173 – Vessel Numbering and Casualty and Accident Reporting They confirm the vessel is registered in a particular state and that the owner has paid the required fees.
The format is the same nationwide: a two-letter state abbreviation, a middle group of numbers (sometimes with letters), and a final letter group, separated by spaces or hyphens. A Florida boat might read “FL 1234 AB.” The characters must be plain vertical block style, at least three inches tall, in a color that contrasts sharply with the hull. They go on both sides of the forward half of the vessel and read left to right.2eCFR. 33 CFR 173.27 – Numbers: Display; Size; Color
A small validation decal sits next to the number on each side of the bow. It shows the current registration period. Without a current decal, law enforcement can stop you even if the underlying registration is valid.
Registration numbers belong to the boat, not the owner. If you sell your boat and the new owner keeps it in the same state, the number typically carries over, though the registration itself still has to be transferred into the buyer’s name. Move the boat permanently to another state and it will need new numbers from that state.
The Hull Identification Number on the Transom
The Hull Identification Number, or HIN, is a 12-character code that works like a boat’s fingerprint. Every boat built or imported into the United States since November 1, 1972 must have one.3eCFR. 33 CFR 181.23 – Hull Identification Numbers Required The manufacturer stamps it on before the boat ever reaches a dealer, and it stays with the hull for life.
Where to Find It
On most boats, the primary HIN is on the starboard (right) outboard side of the transom, within two inches of the top of the transom, gunwale, or hull-deck joint, whichever is lowest. Boats without a transom carry it on the starboard side of the hull near the stern, within one foot of the back end. Catamarans and pontoon boats place theirs on the aft crossbeam within one foot of the starboard hull attachment. A duplicate copy is hidden in an unexposed interior location or beneath a piece of hardware so that if someone tampers with the visible one, investigators can still identify the boat.4eCFR. 33 CFR 181.29 – Hull Identification Number Display
How to Read It
The 12 characters break into four parts, with no spaces or hyphens between them:5eCFR. 33 CFR 181.25 – Hull Identification Number Format
- Characters 1–3 are the Manufacturer Identification Code, a three-letter code assigned by the Coast Guard. You can look any code up in the Coast Guard’s online MIC database to find the original builder.6United States Coast Guard – Boating Safety. Manufacturers Identification
- Characters 4–8 are the serial number, assigned by the manufacturer. The letters I, O, and Q are not used because they look too much like 1 and 0.
- Characters 9–10 are the date of certification. Character nine is a letter for the month (A for January through L for December), and character ten is the last digit of the year.
- Characters 11–12 are the last two digits of the model year.
A HIN like “XYZ12345A519” would mean the manufacturer is “XYZ,” the serial number is “12345,” the boat was certified in January of a year ending in 5, and the model year is 2019.
Why It Matters
The HIN is the single most important number for anyone buying a used boat. It lets you trace ownership history, check whether the boat has been reported stolen, and verify whether any manufacturer safety recalls apply. If the HIN looks altered, is missing, or doesn’t match the paperwork, walk away. That’s one of the clearest signs of a stolen or salvaged boat.
Name and Hailing Port on Documented Vessels
Not every boat carries state registration numbers. Vessels of at least five net tons (roughly 27 feet and up) can be federally documented through the Coast Guard instead. Commercial vessels over that threshold are generally required to be documented; recreational boats of the same size have the option.1eCFR. 33 CFR Part 173 – Vessel Numbering and Casualty and Accident Reporting Documented vessels are exempt from state numbering, which is why you’ll sometimes see a large yacht with a name on the hull and no “FL 1234 AB” on the bow.
A documented vessel displays three things in place of registration numbers:7eCFR. 46 CFR Part 67 Subpart I – Marking Requirements for Vessel Documentation
- The vessel name, in letters at least four inches tall on the exterior of the hull. On commercial vessels, the name appears on both bows and the stern. On recreational vessels, the name and hailing port can go together on any clearly visible exterior part of the hull.
- The hailing port, listing a city and state.
- The official number, assigned by the Coast Guard and preceded by “NO.” This one isn’t visible from the dock. It’s marked in block numerals at least three inches tall on a visible interior structural part of the hull, permanently affixed so that any tampering leaves obvious damage.
The certificate of documentation isn’t considered valid until the vessel is properly marked.
The Capacity Plate
The capacity plate is a metal or plastic placard near the helm or on the inside of the transom. Federal regulations require one on every monohull boat under 20 feet, with exceptions for sailboats, canoes, kayaks, and inflatables.8eCFR. 33 CFR Part 183 Subpart B – Display of Capacity Information Boats 20 feet and longer don’t get a federally mandated plate, which catches some owners off guard.
A capacity plate lists three limits:9eCFR. 33 CFR 183.23 – Capacity Marking Required
- Maximum persons, as both a headcount and a total weight in pounds.
- Maximum weight capacity, meaning the combined weight of people, gear, and engine the boat can safely handle.
- Maximum horsepower, the largest engine the boat is rated for. If the boat isn’t designed for motor propulsion, the plate says so.
These limits aren’t suggestions. Overloading compromises stability and makes a boat far more likely to swamp or capsize. Federal regulations don’t attach a specific penalty for exceeding the plate limits, but many states do, and insurance carriers typically won’t cover an incident that happened on an overloaded boat.
Checking Numbers Against the Paperwork
If you’re buying a used boat, cross-check every number on the hull against the title and registration. The HIN on the transom should match the HIN on the title exactly. The registration number on the bow should match the certificate of number. If anything is off, dig deeper before handing over money.
A mismatched or missing HIN can indicate a stolen vessel, an unreported salvage, or a homemade replacement hull that was never properly documented. Title branding rules for boats vary widely by state, and there’s no national standard equivalent to the one for cars. Some states brand a boat’s title as salvage after an insurance total loss; others have minimal disclosure rules. Running the HIN through the Coast Guard’s database and requesting a full history report is worth the effort on any significant purchase.
And when the boat does change hands, don’t skip the registration transfer. It’s one of the most common mistakes in private sales, and it can leave the seller on the hook for incidents involving a boat they no longer own.