Boat Numbers, Boat Registration Numbers, they are the license plate of a boat it needs to be display and stay there until it is sold or transferred out of the state. Order your Boat Numbers - Boat Registration numbers for your power boat, electric powered boat, jet ski, sail boat (where applies) and other watercraft. Check on your state for size , spacing and placements to meet their regulations. It is the responsibility of the owner to display numbers on the vessel, use permanently applied stick-on numbers/letters on both sides of the vessel. This number always remains with the boat and may not be transferred to another boat. Unlike vehicle registration, some states cannot issue special request or "vanity" numbers.