If your boat is powered by gasoline, it needs to have a ventilation system. That’s because fumes from your engine can collect in the bilge creating the potential for a powerful and dangerous explosion.
The danger is so great that all boats built after 1940 and powered by gasoline are required by law to have a ventilation system. There are two types of ventilation systems: natural and powered.
A natural ventilation system consists of a minimum of two ventilator ducts—an intake duct to bring fresh air into the bilge and an exhaust duct to remove fumes from the bilge. Air moves through the ducts as the boat is in motion. Each duct is also fitted with a cowl, or a hood-shaped covering, to help increase airflow.
In a powered ventilation system, one or more powered blowers does the work of circulating air through the ducts.
Powered ventilation systems are required on boats built after 1982 with installed fuel tanks or an enclosed engine.
It's important to note that boats with powered ventilation systems should be turned on and let it run for four full minutes before starting the engine! This ensures all gasoline fumes have been removed before ignition.