Depending on the size of your boat you may need more than one. Boats less than 26' have to have at least one B-1 fire extinguisher on board. Boats 26'-40' need to have at least two B-1 fire extinguishers on board.
Graphite is an electric conductor, consequently, useful in such applications as arc lamp electrodes. It can conduct electricity due to the vast electron delocalization within the carbon layers (a phenomenon called aromaticity).
These two elements are the best conductors in the metalloid group. Carbon conducts electricity and is classified as a semi-metal when in the form of graphite. Although it conducts electricity and heat like a metal or metalloid, graphite is not used commercially as a conductor. Instead, its softness makes it an effective lubricant for engines and industrial machinery.