Chris Riley by Chris Riley Updated on June 28, 2020. In

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Chapter IV – Legal Requirements

Section 2d – Required Equipment


All vessels built after April 25, 1940 and which use gasoline for electrical generation, mechanical power or propulsion are required to be equipped with a ventilation system. The ventilation system may be either natural or powered:

natural ventilation system consists of at least two ventilator ducts, fitted with cowls or their equivalent:

A minimum of one exhaust duct installed so as to extend from the open atmosphere to the lower portion of the bilge; and

A minimum of one intake duct installed so as to extend to a point at least midway to the bilge or at least below the level of the carburetor air intake.

powered ventilation system consists of one or more exhaust blowers. Each intake duct for an exhaust blower should be in the lower one-third of the compartment and above the normal accumulation of bilge water.

NOTE: Boats built after July 31, 1980, which contain power exhaust blowers in gasoline engine compartments must have the following warning sticker near the instrument panel:





Backfire Flame Arrestor

boating safety course Flame ArrestorInternal combustion engines can backfire. In order to prevent flames from the backfire causing a fire onboard, an approved Backfire Flame Arrestor must be attached to the air intake with a flame tight connection. Flame arrestors must be in good and serviceable condition and approved by the USCG, Underwriters Laboratories (UL 1111) or the Society of Automotive Engineers Standard (SAE – J-1928). All motorboats have this requirement except outboards and diesels.

It is very important to insure that your Flame Arrestor is clean and undamaged. If there is a hole in the grid, or oil or gasoline in the grid, or if it is not properly attached, it will not work correctly. To clean the flame arrestor, remove it and wash the heat dissipation grid with soap and water. Let dry thoroughly and reinstall. Make sure that the arrestor has a flame-tight connection.

You, the owner of the boat, are responsible for keeping your boat’s ventilation systems in operating condition. Make sure openings are free of obstructions, ducts are not blocked or torn, blowers are operating properly and worn out parts are replaced with equivalent marine type equipment.


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