Earth to Ground


I have been reading your comments on problems whereby the boat temperature gauge over-reads when navigation lights are put on. I have tried to find the faulty earth without success.

Can I simply bring a new earth wire from the battery to a new busbar on the dash and remake all the earth connections to the instruments (including the temp gauge) from that busbar? Is there anything I need to be careful of in doing this and should this cure the problem?

Your help would be much appreciated.


Hi Richard,

Your proposed solution will work great. The only concern would be the additional ground wire connected directly to the battery. I’m not a big fan of small and large wires connected directly to the battery. The connection is either too tight for the small terminals or too loose for the large terminals. If you are connecting directly to the battery, I would either put a zip tie or tape around all of the wires that connect each post of the battery to ensure that all positives stay segregated from the negatives. An accidental ground wire touching the positive will cause an immediate fire.

Hope this helps,


Boat Wiring Help and Advice

Welcome to the web’s most visited site for marine electrical information and answers.

For your reference, we offer boat wiring information about everything from shorepower installation to wire gauge calculations to standard boat wiring colors. To find the info that you need, just use the search box.

Or, if you need more specific information about a project, we offer free boat wiring help from Kevin Hannula, one of the industry’s most respected marine electrical geeks nerds authorities.

If you aren’t able to find the information that you need, please send an email to

Melting AC

Hi Kevin

I purchased an old 1989 cruiser, a Regal 280 Commodore, and tripped the 20 amp dockside breaker while using a hatch a/c unit and an electric kettle. I have 30 amp service in the boat.

I reset the breaker and then the AC electric system worked for a few minutes and then went dead. Neither the dockside breaker nor onboard breaker tripped, but we smelled a burning smell. I immediately unplugged the AC system and looked behind the AC panel.

At the main breaker switch where the shore power comes in, I found the white wires melted and melting damage to the black wires. I can fix all the wires, but there is also some sort of capacitor that was wired as a jumper between the green and white wires and it is not in the wiring diagram of the boat. It looks like it has been burned out. I want to know what to replace it with, and then if this overall problem is something that points to the result of another problem or if it may have been some old wires getting warm and then touching.

I can replace everything as it was once I know what to put between the black and green wires, but don’t want to do that and then plug it in if there may be other issues that need addressing.

Thanks for your help.


The only connection in your panel between the neutral and ground would be a reverse polarity indicator. Instead of a light, some boats have an alarm. Some of the piezoelectric alarms look like capacitors.

Hope this helps


Probably Polarity


I need your assistance with my boat wiring.

I have changed trolling motor batteries in my boat and since, I have burned 2 twist plugs. My cables aren’t marked so is it possible I may have crossed them or is that something that would cause my dilemma.

What could be causing me to burn the plug? It has a 4 wire Marinco outlet.

Thank you


On a 12/24 marine electrical system, wiring the batteries is critical. Use a meter (not a test light) to determine if the polarity is correct and the battery cables are correctly connected.

The circuit protection in the positive leads at the battery should trip before you burn up the plug. If you don’t have fuses or breakers at the battery, now is a great time to add them.


Lingering Light

Boat Wiring Guys,

I put in new VHF radio into my sailboat. The installation seemed to be successful except...

Now when I turn off the marine electrical panel switch for the VHF, the green light from the breaker goes out but not right away, slowly turning off in about half a second.

Is there any problem with this? Did I screw something up?



It is not a problem.

The light in the switch gets power when the output side of the switch has power. The residual light is caused by a capacitive charge that is in the VHF radio. This capacitor in the radio helps with noise and voltage spikes but will give the appearance of voltage on the power wire which makes the light stay on.

Hope this helps