Grounding of instruments in steel boat


Furuno Super Fan
Hello all,

I have noticed that several of my Furuno's equipment have a small screw with a Earth sign on it, presumably for bonding to the mass in a plastic boat; but i am wondering if i should tie all equipment having this characteristic to the metallic hull of my boat ? Right now the only equipment which is electrically connected to the metallic hull is the isolation transformer (AC) and the inverter.

Does the bonding of equipment to a common mass is for balancing the electrical potential or is it to be able to better survive a lightning bolt if it ever occurs ? If the later, then not sure the bonding would help because the boat is metallic, if hit by ligthning the current will flow outside of the hull (faraday cage principle).

Any information regarding good practices for installation on Furuno's equipment on a metal boat are welcomed,


The data communication voltage level between the different devices on your vessel is typically at or below 5 volts DC. Voltage noise or voltage transients, even as low as a couple volts, can disrupt this communication.

As I'm sure you know, depending on the quality and age of the wiring on the vessel, you can get different voltage reading at different locations throughout the vessel. These voltage differences, along with the interference referred to above, can impact the performance of each device in a different way and cause undesirable functional anomalies.

By bonding all the devices to a single, (earth) connection point, all equipment is subjected to the same interference. This should eliminate any additional problems caused by voltage differentials between devices.

Bonding is also done for safety reasons, especially in cases where higher voltages are present.

There are cases where bonding all devices together causes more issues. If the source of the noise or interference happens to be one of the devices you have bonded with the others, they all may begin to have problems. This can be the case even when the device causing the problem, remains unaffected by the interference it generates.
In these cases, common bonding is best avoided.

In closing, when it comes to lightening, all bets are off. "Protecting" an electronic device from lightening is going to take a lot more than just connecting a small piece of wire between it and an earth ground.

I hope this helps.