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,


LED Upgrade Wiring


I have an older Sanpan pontoon boat that has the original under bench courtesy lights. LED lighting from Vista Manufacturing

I was wondering if can I replace them with LED lights without rewiring? Can splice the wires from the boat’s old incandescents onto the new LEDs?



Hi Syd,

Your new LED lights will draw considerably less power than the old lights, so you can certainly use the existing boat wiring.

Keep in mind that LEDs are polarity sensitive. That is, if they don’t work at first, you may need to swap the wires to make them turn on.

Finally, you can splice them in with the old lights if you wish.


Dimmer Replacement


I have an old Guest dimmer switch that needs replacing – and I can not find a replacement switch for it.

My switch has three wires coming off the back of the switch, two black and one red. I know one goes to the light, the other to the hot, where does the third wire go? And, can I wire the two blacks together? The only 12v low amp switch I can find all have only two wires, can I use these and how to wire them up. Do I have to re-wire the boat’s entire overhead lighting system to wire up with two wires?

I still want to use a 12v dimmer switch with off and on, and not just an off and on switch only, hope all this makes sense?

Have a great day


Hi Roy,

Depending on the dimmer type, the third wire was either a ground or second tap on the variable resistor that would would give the opposite output of the dimmer wire (basically one output would increase the voltage – brighter – and one would decrease the voltage – dimmer).

The new two wire dimmer will work great. Make sure the wattage rating on the dimmer is at least as large as the wattage of your boat’s lights.

Hope this helps,


Wire Whereabouts


I recently bought a 2007 Smokercraft SunChaser 820. The stereo didn’t work when I bought it – a SeaWorthly SEA MBB126 radio with an amplifier. Sunchaser pontoon

I unplugged the amplifier connection from the boat wiring then also lost my front front red and green navigation lights. After successfully connecting the speaker wires to the new Sony harness, I now can’t seem to find the old wires to splice my battery and ignition wires from the new – or figure out how to get my navigation lights back on. I am a marine electrical beginner at best.

I realize the radio needs power and battery to backup memory. Now that I can’t find any wires from the old amplifier, what is the easiest way to run a line to power and battery to get the radio working?

Any help would be greatly appreciated.


Hi Bob,

My guess is the forward navigation light wires were connected with the same plug as your forward speakers. Smokercraft is a first class boat builder that uses standard boat wiring colors, which means Gray/Green for forward navigation light power and black for ground. The speaker wires will be a different type of wire that will not match the rest of the normal boat wiring.

The ignition switched power wire is going to be purple and most of the time they use yellow or red/yellow for stereo memory.

If you are running new wires back to the battery, make sure to add an in-line fuse or circuit breaker at the battery. You wouldn’t want you new wire to go up in smoke and disappear like the old ones.


12 Volt Out


I recently bought a used 2006 Sunchaser pontoon boat.

It’s a really great boat, but there is a boat wiring issue. All of the marine electrical works except the navigation lights and the 12 volt adaptor. I know the lights can be something as simple as a blown bulb. What could be the problem with the 12 volt outlet? Marinco outlet



Hi Bryan,

The 12 volt outlet probably has a blown fuse.

Check the fuse panel under the helm. If all of the navigation lights do not work, then it is probably a blown fuse also. Replace the fuse, if it still blows, trace the marine wiring from the switch to the lights to locate the short.

Hope this helps,