A luxury motor yacht is basically a “powerboat,” albeit on a much grander scale. And, the power behind the power is your yacht’s electrical system. Without your yacht’s electrical system up and functioning, its motors would fail to start, its computers would not work, basically, she would be dead in the water.

The marine electrical system on a modern motor yacht can be very complex, involving multiple circuits, batteries, isolators, chargers, distributors and more!

So before we can discuss troubleshooting problems with your electrical system and what you can do about them, you need a little basic understanding of electricity and electrical systems.

Marine Electrical Systems

Let’s start with some basic terminology you will need to understand before you can diagnose, and/or fix any problems with your yachts power systems.

  • Load -The “load” is any gear or equipment that the system is required to power, lights, radios, heaters, generators, motors, if it requires an electric current, it is part of the systems “load.”
  • Ohm – Is a unit of measure of the electrical resistance in a wire or cable.
  • Ampere (Amp) – The amount of current flowing through a medium is measured in “amps.”
  • Volt – One voltis defined as the difference in electric potential between two points on the load.
  • Resistance – The opposition to electricity flowing through a wire, created by wire material, diameter, and length.
  • Short Circuit – When electricity flows along an unintended path, usually due to the accidental contact of components and consequent unintentional diversion of the current.
  • Ground Fault – A condition which allows a lower resistance path to ground somewhere other than the actual ground wire.


Now that you have same of the basic terms down, here’s a brief overview of the main electrical components commonly found in modern motor yachts.


Of course, batteries play a big role in your boat’s electrical power plant. There are usually two types of batteries found on power yachts: cranking batteries and storage batteries.

Cranking batteries are what provide the “juice” for your engines to turn over. Once the engines are up and running, the cranking batteries are not “in use” and are charged by the vessel’s alternators.

Storage batteries are what provide electrical power to your yacht’s lights, and run all of the electrical equipment and electronics on board. Storage batteries, particularly on large motor yachts that require a lot of power and amperage, are known as “deep-cycle” batteries. Deep cycle batteries can retain their charge for a long time, and can be depleted and recharged over and over again with little or no damage.



An isolator, or more specially a “battery isolator,” is what directs the flow of power from the ship’s alternators to a specific battery or batteries. Isolators are also there to make sure that batteries do not discharge from one to the other during operation.

Circuit Breakers

You are no doubt familiar with the circuit breakers in your home. The circuit breakers on your yacht serve the same purpose. They are there as automatic emergency power cut-offs in case of a power surge, which protects critical electrical system components from damage.


Again, like the fuses in your home or car, the fuses on your boat are your electrical system’s critical component’s first line of defense against spikes or irregular disruptions in power.

marine electrical system

Most Common Problems With Your Boat’s Electrical System

As you might imagine, seawater and electricity do not mix very well. The biggest problem facing your electrical system and electronic components is corrosion. Most of the time that there is a problem, or “short” in your electrical system it is due to a mechanical failure, such as a loose wire, or corroded circuit, and not a serious fault in the system itself.

When trouble shooting any problem with the electrical system such as a motor, or other component that will not start, check the obvious first. Make sure your batteries are fully charged. Check all the terminals for tight connections and for any signs of frayed wires or corrosion.

If the problem is that your engine will not start, check the following:

  • Is there enough gas in the tank?
  • Is the throttle in the neutral position?
  • Check for corrosion or frayed wires on the starter cable


Electrical Systems Planned Maintenance and Repairs

The marine environment can be especially harsh on the components of your boat’s electrical system. Most of the time that there is failure in any of the components of the system, it can be traced to corrosion or buildup of dirt on terminals or connections. The harsh sea environment can also lead to loose connections, frayed wires, damaged insulation, loose fuses, and fault switches.

Keeping the components of your motor yacht’s electrical system inspected, cleaned and fully operational, is all part of the planned maintenance you will find as part of our On Demand yachting solution.


Operating a motor yacht can be costly. You can reduce your expenses, and avoid costly repairs by keeping her well maintained. On Demand yachting from FYM can help. If you would like to learn more, or if you have any questions or comments about this blog post, do not hesitate to contact our Yacht Management specialists, or call us at (954) 900-9968.