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).
In spherical form, the graphite exerts a minor influence on the properties of the steellike matrix because in that form the graphite-to-metal contact area is at a minimum. It is relatively economical to produce and finds application in many industries. Ductile iron is similar to other high-carbon, high-silicon alloy with respect to corrosion resistance, sliding wear, and machinability except insofar as the shape of the graphite alters these characteristics.