Grounding to keel bolt help

[tahoemark]

In cleaning the bilge of my J100 the ground wire became dislodged. I think it was already severed as me and a sponge should not be able to break it. I didn't want to remove the keel bolt nut and was going to use another ss nut on top of the existing nut and use a ring terminal for the ground wire between the two nuts. However, I haven't found any source for ring terminals large enough for the 7/8" bolt (largest seem to be 1/2"). If it was solid wire I could just loop that around the bolt and tighten the nut, but as it's stranded wire I'm not sure what to do.
Unrelated, but why do I have rust(?) stains in the bilge since everything is stainless and fiberglass?? Picture attached (if I did this right).

 

[TENACITY CS36T]

Drill and tap the flat top surface of the keel bolt, then you can use an easily acquired ring terminal, the connection will benefit from staying dry, depending on how much water is usually in the bilge etc.....

 

[Don S/V ILLusion]

Or used tinned stranded wire and solder it into a solid mass. If you do this, make sure to mechanically fix it so as to preclude bending at the solder joint.

 

[dlochner]

Get the largest ring terminal you can find, probably ⅜" and drill it to ⅞". Try to find one with enough metal to drill.

Take a short piece of SS flat bar, drill a 78/8" hole for the keel bolt and a hole for a bolt to attach the bonding wire.

It is a good idea to periodically retorque the keelboats. When the boat is on the hard retorque them and reinstall the cable.

Are you sure that the brown is rust? Could it be discoloration from water the boat sits in?

 

[tahoemark]

Thanks for the ideas. The bilge is usually dry in this area, however with recent rains I seem to have a leak that I have yet to find. (Boat is in salt water and there is no fresh water plumbing so water is from the rain). So I'm puzzled on the stains.

 

[tahoemark]

I like the tapping idea, but wouldn't drilling a ss bolt be hard?

 

[jibes138]

Stainless Steel is a very bad name for the material as it makes people think it is impervious to rusting. The proper name in specifications is CRES or Corrosion Resistant Steel. There are a broad assortment of CRES materials, some are more resistant to corrosion than others. If you are on the hard maybe take off the nuts and pull off the backing plates and see whats underneath. If just a light surface rust, a little polishing will clean them up then rebed them. See if you have any corrosion of the bolts under the nuts. While you have a backing plate off drill a hole in it and tap it near one of the corners where you have some room then you can connect your ground wire to that with a short screw and a ring terminal. Once connected just make sure you have connectivity between the ground wire and the keel bolt with a VOM.

 

[justsomeguy]

While you have a backing plate off drill a hole in it and tap it near one of the corners where you have some room then you can connect...

Certainly easier than tapping the keel bolt, I would think.

 

[Franklin]

My boat has a hole in the metal backing plate with a shallow screw attaching the wire. This allows me to replace the wire without having to mess with the keel bolt. The wire lasted until last month (20+ years) with it constantly sitting in salt water so I don't think it is a bad idea. I am waiting to replace it until I get to a place where I can buy proper marine grade wire.

So, if you think you can drill into the plate and not go past the plate, I would suggest that. That will allow you to check the bolts from time to time without messing with the wire.

The crack would worry me as well as the rust stains so I would use phosphoric acid to remove the rust stains from the fiberglass and see if they return (also make sure no other metal falls into the bilge as that has been a problem for me). If the rust returns returned then I would put the boat on the hard and drop the keel to inspect it all including the fiberglass of the area.

 

[tahoemark]

I'm in SoCal, so boat is in the water year round. Drilling in the backing plate sounds more plausible (I think). Franklin, that isn't a crack but just ripple in the coating that they used inside the bilge. If you look elsewhere you might notice some wavy, lumpy looking application.

 

[njlarry]

Rust stains look to be from the corroded wire. Might be difficult to drill and tap plate while in the boat. An easier option would be to remove the wire from the bolt, retorque, add a thin stainless plate that you have added a tapped screw hole to, then lock that in place with a second nut on top.
However, galvanic corrosion is a tricky subject. Hopefully someone knowledgeable will comment on the advisablity of grounding to a keel bolt for other than lightning protection.

 

[Crazy Dave Condon]

Not sure if Fastenal sells those. Have you tried West Marine as they many years ago had the larger sizes.

 

[RoyS]

I assume that cable is to connect your mast to the keel for lightning protection. If so, keep in mind that the cable terminal and any associated hardware should be able to carry high current in the event of a lightning strike. Cable terminals are often available in light gauge and heavy gauge for a given cable size. Be sure to get a heavy gauge (high current) model. The terminal that broke was probably the wrong type anyway. A thin light gauge terminal while providing a good low resistance reading on a meter will simply vaporize in a lightning strike.

 

[Scott T-Bird]

What is the gauge of that wire? If you do some reading about grounding for lightning strike, you will find so many varied opinions that you will probably not know what to think is correct. But in some of my reading, it seems that the ground cable should be at least 50 mm squared in cross-sectional area. I've also read that the cable should be no less size than 4 AWG. But 4 AWG is only 21 mm squared so 1/0 would seem to be more appropriate. Your wire looks like it is no more than 10 or 12 AWG (if that?) and I find it hard to believe that it would be there for any other reason except for "show". I know the one on my boat is about that size so I place no merit on it at all for protection.
That said, there really is no reason why you can't remove that nut, if for no other reason than to remove the remnants of the old wire. The keel will not be compromised. Heck, you could probably remove the nuts from all of the keel bolts as you are sitting in your slip and the keel wouldn't fall off. I'd bet it is bonded with adhesive/sealant (like 5200) between the stub and the keel ballast, and the studs would be bonded within the fiberglass as well. But it is true that you shouldn't replace the cable connection under the nut. I don't see any reason why you couldn't add a second nut on top and sandwich the ring between them. I agree that drilling into the square plate is impractical because they are too small for the correct sized stud and drilling into the top of the stud would be ridiculously hard to do. Why would you do that anyway? A hole in the stud would compromise the stud and make the nut completely useless for strength. Besides, why introduce more potential for crevice corrosion? If you really feel a need to replace the wire, you may as well size it correctly. You'd end up with a ring terminal for a battery stud, no doubt, which should be large enough to fit over the keel bolt stud.
The stains may not even be rust stains. Those weeps appear to come from some hidden areas. If you have any persistent leaks, which you may have given the water in the bilge, you may have some wood somewhere that is releasing those stains as it gets saturated during rain events. I know that it has happened in my bilge and that is exactly what it looks like.

 

[jibes138]

Drilling and tapping the stud to a depth less than where the nut sits will not effect the strength of the stud. The portion above the nut is not contributing to holding on the keel and a racer might consider cutting them shorter to reduce weight. I actually thought that was an innovative way to solve the poster's problem. That ground wire looks like a typical household ground wire with the green insulation, it is probably solid copper. Given the greater amount of staining on the right side of the picture it looks like water is coming in from the large hole next to that keel bolt, so might be worth a look in there to see what's going on. The staining might just be from algae and other crud growing in the stagnant water.

 

[dlochner]

A close examination of the wire end shows little strands sticking out, so it is probably stranded wire, maybe 10 ga.

Trace the wire back, it may not be for lightening protection, but a bonding wire connecting all the below water metals.

Scott, mentioned that the discoloration could be rotting wood core. He may be on the right track. I've sailed on a few Js and almost everyone had a soft deck, usually near a high stress area like stanchion bases, winches, etc. Js were meant to be sailed hard and they usually were. The good news is that they don't use headliners so deck repairs and core replacement can be done from the bottom up. Messy but easier than tearing up and replacing decking.

 

[Bob J.]

Here's what the bonding connection to keel bolt on my boat looks like.

 

[tahoemark]

Success. well I hadn't read Scott T-Bird's post this morning when I worked on the boat, but did essentially what he suggested. I loosened the keel bolt nut to clear whatever fitting they had used to ground. It turned to be a copper ring terminal that was spread to fit the 7/8" bolt. I was able to clean up the ring terminal and re-use it. I reinstalled it between the existing nut and a new nut that I put on top. The ground wire is going to the engine block, which has several other ground wires connected on the same stud. Wire looks to be 4AWG. Dlochner, good suggestion that it might be from wood. It is supposed to rain Monday, an I intend to the boat and see if I can figure where the water is coming from.
Thanks everyone for suggestions and support.

 

[dlochner]

If that wire is connected to the engine block along with several wires, it is most likely a bonding wire designed to keep all underwater metals at the same electrical potential to combat galvanic corrosion.

Good luck on finding the leak.

 

[heritage]

For your peace of mind, remove the nut on the keel bolt on the right side in the pic. It looks suspiciously like what mine looked like: Shiny on upper side of bolt and rust stains around the base of the large washer. This pic shows one of the bolts with moderate corrosion taking place under the nut. A couple of the bolts were severely corroded and one broke as I removed the nut. On close inspection, all of the corrosion took place inside the bilge. There was no water coming in from the keel stub.