Aluminum hull connected to battery negative?

[santurinos]

We?re just about finished with rewiring our Tracker PRO V17 boat.
Everything is working perfect, the instruments, the lights, the bilge pump and live-well.
While testing the circuit, I figured that the negative pole from the battery is connected with the aluminum hull. This could be because there is a radio installed or there is somewhere a short.
My question is:
Is it OK for the hull being connected to negative?
Thank you for your help ? have a nice start-up into the new week? Santurinos

 

[jspriddy]

Re: Aluminum hull connected to battery negative?

There's all kinds of threads on this-just do a search for "ground aluminum hulls" or something similar. It's my understanding, and I'll probably be corrected, that your hull is "bonded" (which seems to be the same thing as grounded) through your motor's attachment to the hull and its electrical system.

I think the main thing is to NOT use the hull for a ground on accessories as you would on an automobile. Everything must have a direct ground to the battery. Something about some kind of gremlin (called "Electrolysis", it must be an ancient Greek gremlin) that will eat your boat while you're going down the river (and I assume also going "up the creek", not to mention the proverbial paddle) and then the alligators will eat you.

So it's not a good thing to do. NOT have a ground, that is.

John

 

[John_S]

Re: Aluminum hull connected to battery negative?

After reading some posts here, found that indeed my alum hulls get "grounded" to neg wire on elec start outboards. I can't say I have found mfg evidence that you can put your finger on it as intentional and nothing in boat or outboard manuals. I use "grounded" in a loose sense. A number of the places I tested on the hull had higher resistance than anything you could technically call grounded.

 

[Silvertip]

Re: Aluminum hull connected to battery negative?

1) You do not ground electrical accessories to the hull. They get connected to a buss that is ultimately connected to battery negative.
2) The large negative battery cable connects to the engine block. The engine itself is bolted to the transom of the boa. That physical attachment means the negative terminal of the battery gets connected to the hull by default but as such, may or may not be a very good ground because of paint, corrosion, etc.

 

[minuteman62-64]

Re: Aluminum hull connected to battery negative?

It's called "bonding," and, based on the posts I've looked at, both on this site and some devoted to aluminum boats, about half the boaters think it is a good idea and half think its a terrible idea. In your case, the hull connection may be delibrate (such as a jumper wire directly from the battery negative to the hull) or incidental (such as the motor mounting described above).

On my boat, the motor is mounted on a rubber transom pad, and, I librally dosed the mounting bolt holes with silicone - result was no electrical connection between the hull and battery negative. My OB manual recommended a "bond," so I went with the 50% that favored "bonding" and hooked a wire from the battery negative to an interior panel that is welded to the hull (the accessories are not grounded to the hull - all have dedicated grounds running through the fuse box back to the battery negative). So far the hull hasn't dissolved - I'll keep you posted.

 

[jspriddy]

Re: Aluminum hull connected to battery negative?

Honestly, I see no advantage to grounding the aluminum hull and a bunch of possible negatives.

Um. Would you then advise insulating the hull from the motor? I see no need for the motor, since it has its own ground, to be bonded to the hull.

John

 

[jspriddy]

Re: Aluminum hull connected to battery negative?

Oh. Mine's never in water. I just keep it in the backyard to work on. My wife said I should have just bought a new one. I told her that was just like a woman, always wanting to deny a man any fun.

Seriously, I don't keep it in a marina, and use it infrequently. I don't guess it would be worth the effort.

Thanks,

John