Which way are most bilge blowers installed? Are they set for the blowers to pull air out from the bilge and exhaust outside or are they set for the blowers to blow air into the bilge while taking the fresh air in from outside.

Out of the bilge.

Exhausting from the bilge with the inlet hose at a low level. The idea is that vapours will be strongest near the puddle of fuel that leaked into the bilge! You also don't want to pressurize the engine compartment in any way that might force contaminants into the passenger area.

Do you know why they say to run the blower for a few minutes? Approximate volume of engine compartment on twin engine boat is 120 ft3. Average bilge blower with some flex duct on it might only move 60 CFM. Assume only 50% ventilation efficiency and you need at least 4 min to change the air in the compartment once.

For less than $200 you can buy a gasoline fume alarm that will also turn on your bilge blower automatically.

From west marine http://www.westmarine.com/webapp/wcs...allpartial/0/0

They are very sensitive, mine kept going off at cold start, turned out an exhaust manifold gasket was leaking.

No boat should be without one IMHO

Thanks everyone for your help.