When must a boat have a fire extinguisher on board?

A boat must have a fire extinguisher on board when it has an enclosed engine compartment because this area can have a higher risk of fire due to the presence of fuel and electrical systems. Enclosed engine compartments contain flammable materials and provide a confined space where heat and fuel could ignite a fire. Having a fire extinguisher readily available in such situations is essential for safety, as it allows for immediate response if a fire occurs.

Other situations, such as traveling in heavy traffic or having an open deck, do not inherently increase the risk of fire in the same way an enclosed engine compartment does. While safety regulations can vary and there may be other considerations about fire safety on boats of different sizes and configurations, the requirement for a fire extinguisher directly relates to the enclosed space's potential hazards. Therefore, the presence of an enclosed engine compartment is the key factor that necessitates having a fire extinguisher on board.