Put the fill cap on tightly to prevent vapors from escaping.
Open all windows, ports, doors, and other openings.
If your boat is equipped with a power ventilation system (exhaust blower), turn it on for at least four minutes before starting your engine. This will help eliminate fuel vapors in the bilge.
Before starting the engine, sniff the bilge and engine compartment for fuel vapors. Continue ventilating until you cannot smell any fuel vapors. Consider installing a gas vapor detection and alarm device.