Blower question - run all the time or just at cranking?

I agree, but let's remember the primary reason for running the blower prior to starting is to evacuate the possibility of any fuel vapors. At a young age I was taught to open the engine compartment on first use of the day to inspect engine for oil or fuel leaks, check oil and coolant levels (if applicable). This safety measure will also evacuate the engine compartment prior to cranking. I run the blower during this engine inspection process and during all operations below 25 mph. Once up on plane and at cruising speed the fresh air ventilation system will continue to evacuate the engine compartment of any volatile fuel vapors while supplying the engine fresh air required for operation. In warmer climates blower usage is extremely important as today's fuel vaporizes at a lower temperature.

 

I run my blower prior to starting it. I don't otherwise run it, except when idling out of the marina.

 

And off during refueling! Walt has it correct, I run ours anytime there is not enough air flow to ventilate the engine compartment.