Table of Contents

Download the PDF Version

It's the Law

Sound-Producing Devices


In periods of reduced visibility or whenever a vessel operator needs to signal his or her intentions or position, a sound producing device is essential.

If on State Waters or on the Mississippi River, Missouri River, or Federal Reservoirs*

Less than 16 feet long (Class I) None required, but at least a whistle is recommended
16 feet long or longer but less than 26 feet long (Class II) Whistle or other sound-producing device required
26 feet long or longer (Class III or IV) Whistle or other sound-producing device and a bell required
* Federal reservoirs in Iowa include Saylorville, Red Rock, Rathbun, and Coralville Reservoirs.

If on Federally Controlled Waters

Less than 65.6 feet long (includes PWCs) Whistle or horn audible for at least one-half mile required
65.6 feet long or longer Whistle or horn and a bell audible for at least one mile required

Sound Signals

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

Changing Direction

  • One short blast tells other boaters, “I intend to pass you on my port (left) side.”
  • Two short blasts tells other boaters, “I intend to pass you on my starboard (right) side.”
  • Three short blasts tells other boaters, “I am operating astern propulsion.” For some vessels, this tells 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 sailboats under sail.

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.