Navigation rules require sound signals to be made under certain circumstances. Meeting, crossing and overtaking situations described in the Navigation Rules section are examples of when sound signals are required. Recreational boats are also required to sound signals during periods of reduced visibility.
Vessels 39.4 feet (12 meters) or more in length are required to carry a whistle or horn. Vessels less than 39.4 feet (12 meters) in length (including PWCs) may carry a whistle or horn or some other means to make an efficient sound signal audible for 1/2 mile.
Vessels 65.6 feet (20 meters) or more in length are required to carry a whistle or horn and a bell that are audible for 1 mile. Please note that the bell is no longer required on a boat 12 meters or more but less than 20 meters in length.
These requirements are to enable you to signal your intentions and to signal your position in periods of reduced visibility.
Every vessel is required to carry some kind of efficient sound producing device to signal their intentions as outlined below. Vessels are required to sound signals any time that they are in close quarters and risk of collision exists.
- The term “short blast” means a blast of about one second.
- The term “prolonged blast” means a blast of from four to six sconds.
The following signals are the only ones to be used to signal a vessel’s intentions ( inland rules only).
- One short blast – I intend to change course to starboard.
- Two short blasts – I intend to change course to port.
- Three short blasts – I am operating astern propulsion (backing up).
- Five or more short and rapid blasts – Danger or doubt signal (I don’t understand your intent).
Note: Inland rules use sound signals to indicate intent to maneuver and a response should be received. In International rules the signals are given when the maneuver is being executed.
Vessels indicate their intention to maneuver by using sound signals. If you do not agree with or understand clearly what the other vessel’s intentions are, you should sound the danger or doubt signal (5 short, rapid blasts). Each vessel should then slow or stop until signals for safe passing are sounded, understood and agreed to.
The danger or doubt signal can also be used to tell another vessel that its action is dangerous. If a boat is backing up into an obstruction you would sound the danger signal to warn the operator.