A state-numbered boat carries the number from its certificate of number on the hull. The federal rules set the number's form and how it is displayed; the state issues it.
The form
Every number starts with two capital letters for the issuing state, from the table in 33 CFR Part 173, Appendix A. Then comes either up to four numerals followed by up to two capital letters (NH 1234 BD), or up to three numerals followed by up to three capital letters (WN 567 EFG). The letters after the numerals may not include I, O or Q, which can be mistaken for numerals (33 CFR 174.23).
Several state letters are not the postal code: California is CF, Colorado CL, Delaware DL, Hawaii HA, Kansas KA, Massachusetts MS, Michigan MC, Mississippi MI, Nebraska NB, Washington WN, Wisconsin WS and the Northern Mariana Islands CM.
The display
- Painted on or permanently attached to each side of the forward half of the boat (33 CFR 173.27(a)(1)).
- Plain vertical block characters not less than 3 inches high (173.27(a)(2)). Script, italic and outlined letters do not meet this; the studio offers only upright block faces for the number.
- A colour that contrasts with the background and is distinctly visible and legible (173.27(a)(3)). The rule gives no ratio; the studio warns below 3 to 1.
- Spaces or hyphens between the letter and number groups equal to the width of a letter other than I or a number other than 1, for example DC 5678 EF or DC-5678-EF (173.27(a)(4)). The studio sets each gap to the width of a "0" in the face you chose.
- Reads left to right on both sides (173.27(a)(5)).
- No other number on the forward half (173.19).
Where the hull or superstructure would hide a number, it goes on a backing plate attached to the forward half so it is visible from each side (173.27(c)).