It's the Law: Required Equipment

Sound-Producing Devices

The following requirements apply to vessels operating on Missouri state waters.

• Vessels more than 16 feet but less than 40 feet in length are required to carry on board a whistle or horn to make an efficient sound to signal intentions or positions.
• Vessels that are 40 feet or more in length are required to carry on board a whistle or horn and a bell.

The following requirements apply under federal laws on federally controlled waters.

• Vessels less than 65.6 feet (20 meters) in length, which includes PWCs, are required to carry on board a whistle or horn or some other means to make an efficient sound signal that are audible for at least one-half mile.
• Vessels that are 65.6 feet (20 meters) or more in length are required to carry on board a whistle or horn and a bell that are audible for at least one mile.

Common Sound Signals

Some common sound signals that you should be familiar with as a recreational boater are as follows.

• A short blast lasts one second.
• A prolonged blast lasts 4-6 seconds.

Changing Direction

• One short blast tells other boaters "I intend to pass you on my port (left) side."
• Two short blasts tell other boaters "I intend to pass you on my starboard (right) side."
• Three short blasts tell other boaters "I am backing up."

Restricted Visibility

• One prolonged blast at intervals of not more than two minutes is the signal used by power-driven vessels when underway.
• One prolonged blast plus two short blasts at intervals of not more than two minutes is the signal used by sailing vessels.

Warning

• One prolonged blast is a warning signal (for example, used when coming around a blind bend or exiting a slip).
• Five (or more) short, rapid blasts signal danger or signal that you do not understand or that you disagree with the other boater's intentions.