In motorized vessels, flammable gases can gather in low areas of the engine compartment or bilge the lowest point of a boat's interior hull. . These have the potential to create a powerful and extremely dangerous explosion. As such, a proper ventilation system is required for all vessels built after 1940 and powered by gasoline. Ventilation systems can be natural or powered:
NATURAL VENTILATION SYSTEMS
Minimum of two ventilator ducts (one intake duct, one exhaust duct) fitted with cowls (hooded opening) to remove stagnant fumes.
POWERED VENTILATION SYSTEMS
Required on vessels built after July 31, 1982, with installed fuel tanks or an enclosed engine. Consists of one or more exhaust blowers.
NOTE: Ensure intake ducts are located above the normal accumulation of bilge water. Turn on the powered ventilation system for FOUR minutes before you start the engine, to ensure all gasoline vapors have been removed before ignition.
LET THE POWERED VENTILATION SYSTEM RUN FOR FOUR (4) MINUTES BEFORE STARTING YOUR BOAT'S ENGINE.