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.


Outlets Out


My 1989 280DA Sea Ray’s shore input was plugged into a 110 volt system at my house. The batteries were being pulled down all the time because I was in the process of changing out all the incandescent lights for LED fixtures, and rewiring as I went.

So, I plugged a battery charger into one of my 110 outlets, and turned it on. The battery charger shorted out. After that none of the 110 receptacles worked.

I have replaced the circuit breaker on the main panel, and have replaced the GFI outlets in the boat. (One guy told me it must be the charger/converter (Professional Mariner New Pro 20/35 3 Bank) So I pulled that out where I could get a look at it. However, I get good 12 volt output from it when it is hooked to a 110v source.

I am not sure what else to do.

Any ideas? If so I would sure appreciate your advice.



Hi Ron,

I would start at the panel to see if you have AC power.

Using a meter, check for AC voltage on both the line and load side of the circuit breaker. Also, check for power when a load, such as the charger is connected. If you have power at the breaker, check at all outlets in the series as they make their way to the battery charger.

You will probably find a bad connection in the line between the ac panel assembly and the charger outlet.

Hope this helps,


Gang the Grounds?


I just replaced my boat battery charger with a Guest 2622A.

After more than 24 hours, the #2 red and green lights are on, #1 is green only.

The original charger had three DC wires; #1, #2, GND. Since the 2622A has an additional ground, I jumpered the two DC- together with the ground wire from the batteries connected at DC- #2.

Will this affect the charger? I want to confirm this is ok before looking for other causes.



Hi John,

As long as both ground wires from the 2622 are connected to the common DC ground system it should be fine.

The 2622 is actually has two separate battery chargers inside of it so both grounds need to be connected for the system to work.

Hope this helps,


Three into one?


I have a 1983 Ski Nautique, 351 Ford engine, with a three wire alternator.

I want to convert the marine electrical to a one wire alternator but not quite sure how that is accomplished. On the old alternator there was a green “Field” Wire, a brown “AUX” wire and an orange “Act Output” wire plus a ground connection to the alternator case. The green, brown and wires went to the external voltage regulator.

My thinking is I disconnect these wires from the old alternator and the external voltage regulator and
disconnect the orange completely and run a new cable from the boat battery to the “BAT” post on the new alternator.

Is this correct?

One question I have with this is won’t there be a constant drain on the battery with the alternator hooked directly to the battery?

Thanks in advance for the help.


Hi Joel,

A single wire alternator is simple. They are self exciting and start charging as soon as the alternator is turning. When they stop turning, they stop charging. There is not a constant drain when the boat engine is off.

Remove all of the extra external regulator wires. You can either run a new alternator output wire or just use the orange in your existing engine wiring.


Adding a third boat battery

Hi Kevin,

My boat is a 2005 Sea Ray Sundancer with a single 8.1 liter engine.

I currently have two boat batteries and would like to add a third. I’m not sure how to accomplish this as my marine battery switch is only set up for two batteries.

Is it possible to tie two of the batteries together? If I did would they still charge properly? I’ve looked at
marine electrical isolators but not sure if thats what I need either.

Any suggestions?



Hi Dewayne,

If your goal is to simply add battery capacity to your boat accessory battery, then you can add the third battery by running a ground cable to connect the grounds and a positive cable to connect the positives. I recommend keeping the length to a minimum and using at least the same size wire as the current boat battery cables.

If you are looking for third, separate battery bank, then I would recommend either using an isolator or voltage sensitive relay, a VSR. VSRs are easier to install and more reliable.

Hope this helps,




If I connect two boat batteries together for extra capacity, will the batteries still charge adequately via the charger/alternator?


Hi Dewayne,

Yes they will, but it will take longer for them to fully charge.



I really appreciate the input. I recently installed a larger amp for my stereo and it’s draining my boat’s house battery when I stay out at anchor overnight.

My battery charger will charge up to 3 separate banks. Eventually I’ll figure out how to wire all three separately. Just looking for a relatively easy fix without getting too complicated.

Thanks again!