I purchased a small 12 volt fuel pump at the auto parts store, added wire with battery clips, 5/16" gas hose and the tank fitting that matched the boat's fuel hose connector.
To drain tanks, connect the pump hose with the tank fitting to the boat's fuel hose and put the end of the output hose into a gas can. Then clip the wire to the battery posts. That starts the pump, no switch needed, but a switch could be put in the wire.
Small pumps take some time to move the fuel from tank to gas can, larger pumps would work faster. Depending on the hose length, this pump could transfer gasoline from the boat to a vehicle's tank.