Horn, bell and fog signals by boat length (Rules 33 and 35)

Navigation Rules, lights & bridges · Power & sail

Boats 12 meters (39.4 ft) and over must have a whistle (horn), and boats 20 meters (65.6 ft) and over a bell as well; smaller boats need some other efficient sound signal. In or near restricted visibility, every boat must sound the Rule 35 fog signal for what it is doing, at the set intervals.

What you must carry (Rule 33)

• 12 meters (39.4 ft) or more: a whistle meeting Annex III (33 CFR 86) (Rule 33(a)).
• 20 meters (65.6 ft) or more: a bell as well as the whistle. The bell may be replaced by equipment with the same sound, provided the signals can always be sounded by hand (Rule 33(a)).
• Under 12 meters (39.4 ft): no whistle or bell required, but you must have some other means of making an efficient sound signal (Rule 33(b)).

Underway in restricted visibility (Rule 35)

• Power-driven vessel making way: 1 prolonged blast at intervals of not more than 2 minutes (Rule 35(a)).
• Power-driven vessel underway but stopped: 2 prolonged blasts about 2 seconds apart, at intervals of not more than 2 minutes (Rule 35(b)).
• Sailing vessel, and vessels not under command, restricted in ability to maneuver, fishing, or towing or pushing: 1 prolonged followed by 2 short, at intervals of not more than 2 minutes. The COLREGS add vessels constrained by draft (Rule 35(c)).
• A sailboat under engine, with or without sails up, is power-driven and sounds the power-driven signals (Rules 3(b), 3(c), 35(a), (b)).
• Last vessel of a tow, if manned: 1 prolonged followed by 3 short, at intervals of not more than 2 minutes, right after the towing vessel's signal when practicable (Rule 35(e)).

At anchor and aground

• At anchor: ring the bell rapidly for about 5 seconds at intervals of not more than 1 minute. You may add 1 short, 1 prolonged, 1 short to warn an approaching vessel (Rule 35(g)).
• Aground: the anchor bell signal, plus three separate and distinct strokes on the bell just before and just after the rapid ringing. You may add a suitable whistle signal (Rule 35(h)).
• Fishing at anchor, or restricted in ability to maneuver while working at anchor: 1 prolonged followed by 2 short instead of the bell (COLREGS Rule 35(d); Inland Rule 35(c)).

Options for smaller boats

• 12 meters (39.4 ft) to under 20 meters (65.6 ft): you need not give the anchor and aground bell signals, but if you don't, make some other efficient sound signal at intervals of not more than 2 minutes (Rule 35(i)).
• Under 12 meters (39.4 ft): you need not give the Rule 35 signals, but if you don't, make some other efficient sound signal at intervals of not more than 2 minutes (Rule 35(j)).
• Inland only: a vessel under 20 meters (65.6 ft) anchored in a special anchorage area designated by the Coast Guard need not sound the anchor signal (Inland Rule 35(l)).

The rules: COLREGS Rule 33 · Inland Rule 33 · COLREGS Rule 35 · Inland Rule 35 · 33 CFR 83.03 · 33 CFR 83.33 · 33 CFR 83.35

A plain-language summary of federal rules for recreational boats, checked against the rules’ own text and a second source, and written in our own words. It isn’t legal advice. States add rules of their own, and rules change — the links above go to the current official text.