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).
Why is copper a good conductor of electricity? Because graphite is such a great conductor, it is used in electrical cells. It is also found in motor oil and pencils. Because graphite is soft, it is combined with clay, and baked, and hardened before being inserted into wood for pencils. Graphite is made up of bonded carbon atoms.