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In the Navigation Rules, how long is a 'prolonged blast'?

4 to 6 seconds.

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  1. About 1 second
  2. About 10 seconds
  3. 4 to 6 seconds ✔

Why: Inland Rule 32 defines a short blast as about 1 second and a prolonged blast as 4 to 6 seconds. Getting the lengths right keeps your signals from being misread.

Huh, didn't know that: A power-driven vessel leaving a dock or berth sounds one prolonged blast.

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Why was the boat horn so good at timing? It counted every second.
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References

Answer: 4 to 6 seconds. Inland Rule 32 defines a short blast as about 1 second and a prolonged blast as 4 to 6 seconds. Getting the lengths right keeps your signals from being misread.

  1. 33 CFR 83.32 Definitions, Inland Rule 32 (eCFR) www.ecfr.gov/current/title-33/section-83.32
    The term prolonged blast means a blast of from 4 to 6 seconds' duration.
    Checked 2026-10-08.
  2. 33 CFR 83.34 Maneuvering and warning signals, Inland Rule 34 (eCFR) www.ecfr.gov/current/title-33/section-83.34
    When a power-driven vessel is leaving a dock or berth, she shall sound one prolonged blast.
    Checked 2026-10-08.

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Boating & WaterA boat under 12 meters (39.4 feet) needn't carry a regulation whistle. What must it have?Boating & WaterOn inland waters, what does one short blast mean when meeting or crossing another powerboat?Boating & WaterWhen meeting or crossing on inland waters, what do two short blasts mean?

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