I have just bought a 1985 20' Thompson Cuddy it's the first I/O I've owned. There are 4 vent hoses that go from the vents to the motor compartment and are open ended. One has a blower motor in line and a switch on the instrument panel; I assume this is to provide fresh air or to get rid of heat from the engine compartment, but the fact that it is wired to a manual switch has me befuddled. Do you have to run the blower all the time your running the motor? Thanks in advance, db