An onboard fire is a serious event. If the fire cannot be controlled, where do you go except in the water? The fire triangle consists of fuel, oxygen and heat. All three must be present to start a fire, and the removal of any single one can extinguish a fire.
Fuels, such as gasoline and propane, can be very dangerous if precautions are not taken. The fumes of these fuels are heavier than air and tend to collect in the bilge and other lower areas of the boat. It is essential that you keep these areas clean and free of trash and debris because they naturally are surrounded by oxygen, and all that is necessary to start a fire is heat. This could come from something as simple as a spark from an ignition component. All you did was turn the key to start the engine and boom.
You should read and understand the instructions on your fire extinguisher(s). If a fire starts, you should be prepared and not hesitate. Grab the fire extinguisher, activate it, and direct it at the base of the flames using short bursts and sweeping it from side to side. (More on this in the Chapter on Accidents.)
If underway and a fire starts, stop the boat and position it in such a manner that the fire is downwind. Order everyone to put on lifejackets. If possible, try to turn off the fuel source to the fire. Grab the extinguishers and control the fire.
P. A. S. S.
Aim at base of flame
Sweep side to side