There are multiple answers to the question “what numbers go on the side of a boat?”
A documented vessel number can be on the transom or either side of the boat.
Some states require that state registration numbers be on the side of a boat.
A “Hull Identification Number” or “HIN” is usually found on the starboard (right) side of a vessel’s transom on the upper right.
More specifically, according to 33 CFR 181.219:
“The primary hull identification number must be affixed – on boats with transoms, to the starboard outboard side of the transom within two inches of the top of the transom, gunwale, or hull/deck joint, whichever is lowest.”
“On boats without transoms or on boats on which it would be impractical to use the transom, to the starboard side of the hull, aft, within one foot of the stern and within two inches of the top of the hull side, gunwale, or hull/deck joint, whichever is lowest.”
“On catamarans and pontoon boats which have readily replaceable hulls, to the aft crossbeam within one foot of the starboard hull attachment.”
“If the hull identification number would not be visible, because of rails, fittings, or other accessories, the number must be affixed as near as possible to the location specified (above).”
Furthermore, the duplication HIN has to be affixed on the boat’s interior as well. The HIN number has to be marked in characters that are at least ¼ of an inch high and, if they were to be removed, altered, or replaced, it would be obvious.
To quote again from 33 CFR 181.219:
“The duplicate hull identification number must be affixed in an unexposed location on the interior of the boat or beneath a fitting or item of hardware.”
“Each HIN must be carved, burned, stamped, embossed, molded, bonded, or otherwise permanently affixed to the boat so that alteration, removal, or replacement would be obvious. If the number is on a separate plate, the plate must be fastened in such a manner that its removal would normally cause some scarring of or damage to the surrounding hull area. A hull identification number must not be attached to the parts of the boat that are removable.”
“The characters of each hull identification number must be no less than ¼ of an inch high.”
Use this link to conduct a boat HIN lookup.
If you have further questions about what numbers go on the side of a vessel or anything else related to USCG vessel documentation, contact the Vessel Registrar Center at email@example.com or (800) 535-8570 Monday-Friday, 8 AM to 4:30 PM.