aluminum boat, elec ground is boat?

[geezer]

Hi. Got a 70s vintage starcraft alum boat, lotsa changes made by previous owners, wires in back by 120 I/o looks like bowl of noodles. Was surprised to find while trying to get aft light working that the light is grounded to the boat, like an old car. Is that normal? Is there an electrical field going into the water?

[ontherise]

Does it work grounded to the hull?

[LongLine]

I'd run a ground back to the battery or engine.  There's a thing called "galvanic" corrosion and it'll pit aluminum rather badly.

 

Tom B.

(LongLine)

[smallboat]

Do not use your boat as the ground like an old car. The 12 volt system, and in larger boats the 120 shore power, needs to be isolated from the hull. As Longline suggested, wire all connections in a closed system back to the battery. Don't use the hull. Galvanic corrosion is only one of the problems you will create.

[Frogger]

Bad news, as everyone has said. Lights neg should be to the battery neg and pos to pos side of battery with fuse. Went through some thing similar, creates a hot boat and that galvanic reaction is bad as well. What I found out by going through it is the only thing that is grounded is the motor which in simple terms is from the negative side of the battery to your block, this for an outboard, I would think it would be the same for an I/O. If you want to see how much is going through your boat out put an ohm meter to see, neg on your neg side of your battery, touch the positive to your boats metal. Start turning things on that are electrical. You'll start seeing how your boat lights up. Literally. Oh, yea, forgot, forget trying to catch fish...... Not fun at all. Hope this helps.

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[geezer]

With the light's positive wire to the battery the light comes on without the negative wire connected to anything, so the light bulb' s socket must be grounded through the light's assembly to the aluminum hull. If I make sure every light, etc, has a wired ground am I ok? Is the engine/outdrive providing the ground connection and if so is that normal? Just don't use the hull for negative connections to anything and I'm OK? Thanks to everyone who responded....previous boats were glass, I'm not at all knowledgable about boat electronics.

[Frogger]

Yes to the last question. Only thing that should be grounded is motor Everything else should go back to neg side of battery.

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