Boat Ventilation

Information from the Code of Federal Regulations Title 33 Part 175/183, Title 46 Part 25

Boats that use gasoline for electrical generation, mechanical power, or propulsion are required to be equipped with a ventilation system.

A natural ventilation system is required for each compartment in a boat that:

  • Contains a permanently installed gasoline engine.
  • Has openings between it and a compartment that requires ventilation.
  • Contains a permanently installed fuel tank and an electrical component that is not ignition-protected.
  • Contains a fuel tank that vents into that compartment (including a portable tank).
  • Contains a non-metallic fuel tank.

A natural ventilation system consists of:

Display of Numbers

  • Numbers must be painted or permanently attached to each side of the forward half of the vessel.
  • The numbers must be read from left to right.
  • The numbers must be of a color that is contrasting with the background color; for example, black numbers on a white hull.
  • The validation sticker(s) must be affixed within six inches of the registration number. No other letters or numbers may be displayed nearby.
  • Lettering must be in plain, vertical block characters of not less than 3 inches in height.
  • Spaces or hyphens between letter and number groupings must be equal to the width of a letter other than “I” or a number other than “1”.

Notification of Changes to a Numbered Vessel

The owner of a vessel must notify the agency that issued the Certificate of Number within 15 days if:

  • A supply opening (duct/cowl) from the outside air (located on the exterior surface of the boat), or from a ventilated compartment, or from a compartment that is open to the outside air.
  • An exhaust opening into another ventilated compartment or an exhaust duct to the atmosphere.

Each exhaust opening or exhaust duct must originate in the lower one-third of the compartment. Each supply opening or supply duct and each exhaust opening or duct in a compartment must be above the normal accumulation of bilge water.

A powered ventilation system is required for each compartment in a boat that has a permanently installed gasoline engine with a cranking motor for remote starting.

A powered ventilation system consists of one or more exhaust blowers.

Each intake duct for an exhaust blower must be in the lower one-third of the compartment and above the normal accumulation of bilge water.

For boats built prior to 1980, there was no requirement for a powered ventilation system; however, some boats were equipped with a blower.

The U.S. Coast Guard Ventilation Standard, a manufacturer requirement, applies to all boats built on or after August 1, 1980. Some builders began manufacturing boats in compliance with the Ventilation Standard as early as August 1978. If your boat was built on or after August 1, 1978 it might have been equipped with either (1) a natural ventilation system, or (2) both a natural ventilation system and a powered ventilation system. If your boat bears a label containing the words “This boat complies with U.S. Coast Guard safety standards”, you can assume that the design of your boat’s ventilation system meets applicable regulations.

Boats built after 1980 with remote starters are required to display a label that contains at least the following information:

Warning

Gasoline vapors can explode. Before starting engine, operate blower at least four minutes and check the engine compartment bilge for gasoline vapors.

A documented vessel is not exempt from:

  • Applicable state or federal taxes.
  • Compliance with state or federal equipment carriage requirements.

A documented vessel may also be required to pay a registration fee and display a validation sticker from the state of principal use. Boaters should check with their state boating agency.

A documented vessel may also be required to pay a registration fee and display a validation sticker from the state of principal use. Boaters should check with their state boating agency.

  • The original document (photocopy not acceptable).
  • On board the vessel.
  • Current (not expired).
  • Signed by the Director of the National Vessel Documentation Center.

Documented Vessel Marking Requirements

Hull Display

A documented recreational vessel hull display must:

  • Have the name and hailing port of the vessel together in one place on the hull (usually on the stern).
  • Be in letters not less than 4 inches in height.
  • Be clearly readable.

The marking requirements for a documented recreational vessel state “together in one place on the hull.” Many recreational vessels will place the vessel name and hailing port on the stern, and vessel name on both sides of the bow, which is required for a commercial vessel. Although not required for a recreational vessel, this is an acceptable option.

Interior Display (Recreational and Commercial)

In addition, the vessel must have the official number permanently affixed in block-type Arabic numerals of not less than 3 inches in height, preceded by the letters “NO.” on some clearly visible interior integral structural part of the vessel.

In addition, the vessel must have the official number permanently affixed in block-type Arabic numerals of not less than 3 inches in height, preceded by the letters “NO.” on some clearly visible interior integral structural part of the vessel.

For more information on documented vessels, contact the U.S. Coast Guard National Vessel Documentation Center at (800) 799-8362 or online at www.uscg.mil/hq/cg5/nvdc.