Ground Wire???

Back again. My '78 cajun has a bare copper wire going, from what looks like the 2nd battery, down to the back bottom of the boat next to the bilge pump. The bare copper wire is connected to a brass bolt/screw that goes thru the boat. The reason I'm asking is to find out what this wire is/does but also I think something may be broke off from the outside. I can see a nub of the screw and a half dollar size circle around it where it appears like something was there. Any ideas. Thanx

Sounds like a thru hull ground to me. Most power boats are grounded via the motor and shaft to the water, but you will see an occasional thru hull design.

I have that thru hull ground on my '95. If all you have is a nub, you will want to tap that out and install a new one.

So your saying that a wire goes down from the motor and connects to that brass bolt from the outside then goes thru with that bare copper wire connected to what??? I asked a local marina guy and he said to cut the wire off that it probly does nothing. Do I need it? The boat ran without it. I have a new problem I will post in the Mercs forum. Thanx

There are basically 2 ways to ground a boat. One way is to run a wire to a fitting that runs through the hull to the water. The other way is to run a wire to the motor and basically use its shaft as a path to ground to the water. Sounds like you have the through hull setup.
And yes you need the ground path. Basically what the ground does is prevent you or your electronics from becoming damaged in the event there is a short in the system. If your system does not have a path to a grounding source then it will basically seek out the next best source...which could be you or your electronics. http://www.bassboatcentral.com/smileys/eek.gif

So I would hook the copper wire from the transom to the negative on the battery.? I also have what appears to be a grounding block at the back down next to the bilge pump.

This is what I suggest. Just leave it as it currently sits and it should be just fine. Bucketmouth4 might shed more light on what it is supposed to look like before the piece on the other side of the hull broke away, but you might have a tough time finding an exact replacement. I think, and I mean think, it was one of the 2" or so round plates, but all I have seen these days is the rectangle plates and those are mostly used on bigger boats and sail boats.

Well i cut off the wire, it was only a thin bare copper wire easily replaceable. I did not touch the "broken" bolt. I did put some silicone over, just in case. I have got her running nice now and I havnt had any problems. Is it just a ground for electrical surges as in lighting type situation? There is a "screw" terminal near the motor side of the trim cylinder. Maybe a wire went from there to the bolt, then thru the transom to the copper wire? But then when would that copper wire connect or ground to? If this sounds right then please let me know. Like I said she is running quite well now. I'm kinda proud of myself. http://www.bassboatcentral.com/boardstuff2/beers.gif Thanx

Did the copper wire that ran to the bolt through the hull run directly from your main battery or your trolling motor battery?

My thru hull bolt is just that. It looks like it is just a copper pan head screw.

I have no connection on the outside, which could explain what's broke. I actually have a bare copper wire connected to that bolt on the inside transom well. It is about 3' long and had a loop curled on the end like it was connected to the battery or something? I am finding out that some stuff has been changed over the years. It's a mystery boat. I have zero details or info on any part of it. http://www.bassboatcentral.com/smileys/doh.gif

I had the same. I brass pan head screw through my transom. there was an old wire connector on it but thats it. never new what it was for but now i know. I think i may run a ground wire from all my batteries to it. I did replace it with a new brass one. If i take something off i always replace it.

After connecting all your batteries, will you then also connect it to your motor? Please let me know because I don't have anything hooked up currently. Thanx