I always go back to my Boat Safety Scheme Training when it comes to electrics on older Yachts. Cables can overheat if the cabling on your boat is not sufficient to carry the current. To minimise this risk the cables must be capable of carrying the current and be of the right construction and grade. New electrical installations must use multi-stranded conductors, since solid conductors can easily break where there is high vibration or repeated flexing of a cable.
Fuel, water, heat, oils and other chemicals can all cause damage to your cables, reducing the effectiveness of the insulation and increasing the risk of cables overheating - which could cause them to short-circuit, spark and start a fire. Exposed 240V wiring (see image) can also give people on your boat an electric shock. To reduce these risks all cables must be properly insulated and/or sheathed with a resistant material.
To prevent damage caused by vibration, cables must be securely fixed at approximately 300mm (12ins) intervals, or run in a pipe or trunking which is adequately supported. Also, to reduce the chance of damage to the cables, they must be kept away from other heat sources such as exhaust outlets, cookers and stoves.