How many minutes must a blower be operated before starting a boat?

A blower should typically be operated for at least 4 to 5 minutes before starting a boat's engine. This time allows for the ventilation of any potentially explosive fumes from the fuel system. It's important to ensure that the engine compartment is adequately cleared of vapors to promote safety when starting the engine. Always refer to the specific manufacturer’s guidelines for your boat for the best practices.