If you're talking about the type that use fans that start before the motor will start, it's to dispell any gas or petrol fumes that might accumulate in the bilge before any sparks are generated by the starter motor or ignition
To vent explosive gasoline vapors from the engine compartment.
Turn on the ventilation system before you start the engine; normally on inboard engines which are in a confined space.
Its purpose is very important. It takes care of any residual gas vapors and exhaust them out, so that when you start your boat, you don't blow your own booty out of the water.
To allow the engine to breathe, and help to vent fumes as well.
Mechanical Ventilation System
Mechanical
must have a mechanical ventilation system (EQ-17)
The purpose of a ventilation system is to ensure good airflow into the area where one works or lives. A ventilation system helps air circulate better allowing fresh air to be pumped in.
Mechanical unless your boat was built before July 31, 1980.
Mechanical
Inboard gasoline boats built after July 31st, 1980 must have what type of ventilation system?
Its purpose is to circulate air through engine and fuel tank compartments.
To remove flammable gases