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My trolling motor for my boat has a black and a red connection. The red goes to the positive on the 12 volt battery. The black goes to the negative on the 12 volt battery. Could I connect the black to the giant metal boat I am driving, and then connect the negative on the battery to a different part of the metal boat? Since I use 2 12 volts (one for the trolling motor and one for the main engine starter and aerator) could I use only a single connection from one battery to ground the entire boat?

Or am I doing this all wrong?

Pᴀᴜʟsᴛᴇʀ2
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USER_8675309
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4 Answers4

12

You could do this, but you would not want to. By running current through the surface of the boat, you will induce a voltage potential across it. This voltage potential will cause current to flow from one part of the boat, through the water, to another part of the boat. This will cause electrolytic corrosion, which you definitely don't want.

David Schwartz
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You could do what you are suggesting, but to what end? It seems to me you'd have a much greater chance for something to go wrong. Here are a few things to think about:

If you are running your trolling motor off of both, there is the distinct possibility you'll drain both batteries and then you'd be stranded. Keeping them independent will help ensure this won't happen. Your primary battery should be like what you'd find in a car, which provides a quick discharge with high amperage. The one you are using for your trolling motor should be a deep cycle battery, one which will discharge over a much longer period of time. While they could be tied together, you really don't want to do this.

Another thought is you probably should be running your aerator off of the trolling motor battery. For the same reason as stated above, you can drain your primary battery, again, leaving you stranded. Wouldn't be pretty either way.

You need to charge the one which does the trolling, which means disconnecting it on a regular basis to get it done. Keeping it separate will help in that endeavor, I'd think. The other one will probably be charged by the main boat motor, so you don't have to worry about it as much.

Pᴀᴜʟsᴛᴇʀ2
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If there is no connection to a boat shell at all, then better stay away from grounding. It might be designed that way because you will feed a fish with 12v.. Not sure, but I would concern about it.

Arturs Bolsunovskis
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Apart from the corrosion issues:

If you do this, one day you will be moored to the dock doing some maintenance work on your boat's electrics, when some klutz accidentally drops a live mains power cord extension into the water.

Salt water is a pretty good conductor, so your boat electrics will just have been powered up by a 120V supply when you least expected it. Not a good situation to be in!

And if you are ever out at sea during a thunderstorm, a lightning strike into the water might not do your electrical system any good, either.

alephzero
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