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Required Equipment
Potentially Required Equipment

Ventillation Systems

If you have enclosed areas on your boat, a ventilation system can do many things for you. If you have any gasoline powered engines aboard a ventilation system is a legal requirement. Good ventilation can do many things for you--
help prevent mildew and bad odors, to saving your life by taking carbon monoxide and gasoline fumes out of the boat.

Ventilation systems must have two parts--an air inlet, and a separate air outlet. Both the inlet and the outlet must
have ducts--which are tubes or hoses that extend down into the boat. Ducting for the exhaust must be located in the lower third of the hull--but above any bilge water. Ducting should be routed away from any heat sources, should not
be "kinked", and should be inspected regularly for cracks or debris. (Birds like to make nests in ducts.) Intakes are
usually pointed forward, exhausts usually face aft.

Boats must have a ventilation system that is adequate for the size space the system is used for. Larger boats with larger compartments must have more ventilation--the figure is 15 square inches of opening for each cubic foot of compartment. For most boats that works out to having two inlets and exhausts, with each vent having ducting from
3 inch diameter hose for smaller boats to 5 inch hose for larger boats.




There are two types of ventilation systems that you should be aware of.

Natural Ventilation:

Natural VentilationA natural, or passive, ventilation system consists of vents, cowls and other permanent openings
in the boat that are designed to
let air enter or exit using wind power or the boats' motion to move the air. Natural Ventilation

This type of system is rather ineffective at clearing fumes when the boat is not in motion, so it used primarily for living spaces and tank/bilge areas. It can be used in engine compartments, but only in conjunction with powered blowers.


Power Blowers / Vents:

Power Blowers / VentsA bilge blower is
important not only because it's required,
but because your life
may depend on it.

The USCG stipulates
the use of a mechanical ventilation system for all non-open boats built after July 31, 1981 that run on gasoline.

Even if your boat is older, it still must conform to USCG minimum ventilation levels, and may require a bilge blower to satisfy those guidelines.

Power Blowers / VentsBilge Blowers are specifically designed to clear gasoline fumes from closed compartments. They are ignition protected to prevent sparks, and are built to resist overheating and corrosion. The size
blower you need is determined by the volume of your engine compartment. It is recommended that you use
a blower at least 4 minutes before you ever start the engine, and especially after fueling.


Backfire Flame Arrestor:Backfire Flame Arrestor

With some minor and technical exceptions, every inboard gasoline engine must be equipped with an acceptable means of backfire flame control-or "flame arrestor." This safety device prevents an exhaust backfire from causing an explosion. It operates by absorbing heat.

Flame arrestors no longer require Coast Guard approval; the USCG now accepts flame arrestors complying with Underwriters Laboratories Standard 1111 or Society of Automotive Engineers J1928. When in use flame arrestors must be secured to the air intake of the carburetor with an airtight connection. Elements must be clean, and grids must be tight enough to prevent flames passing through. Cleaning with soap and water is the best way to
maintain its effectiveness.


Don't Leave Port Without It!