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Old 20-07-2007, 12:37   #1
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Taking on water----Zincs

I'm down at the boat this afternoon for a quick fuel filter change, and to resolder a wire going to my starboard bilge pump. I thought I would be finished in 20 minutes, tops... However....

As I climbed down into my starboard hull I sort of noticed it was 1/2 filled with water. Not a good thing. I repaired the bilge pump and took care of the water and found the problem. I have a hull zinc, or had a hull zinc. The bolt attaching the wire inside the bilge was lying all by it's lonesum, and was no longer attached. Where it used to be attached, was a very pretty fountain of water.

The wayward bolt looks to have rusted through?? I'm not really sure. It looks squared up on the business end, but is only 1/4 " long.

I'm mangaged to quiet the pretty fountain of water with a large bolt I had hanging around, and the water ingress is now down to a trickle. I'm at a loss on how to proceed.

Any ideas??

I'm on the boat now..
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Old 20-07-2007, 13:38   #2
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I will let someone more knowlegable that I answer your question. My comment was on your timing.
I would say that you are exceptionally fortunate to have gone there when you did to do some maintenance. Sounds like it way too close to being a completely full hull.
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Old 20-07-2007, 13:46   #3
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Rick,
So we all understand, there is normally a hole below the waterline for a bolt to pass a charge to a zinc? (It does nothing else but serve as fastener and electrical bond for the zinc, right?) And now is it completely gone or just partially missing?

Of course my first thought is where to pull this out of the water to fix it. If the bolt is completely missing then you may be able to get a zinc and a new bolt and put it back together. (I once watched a diver and mechanic change a below the water thruhull without taking a boat out of the water.)

Do you have a digital camera and can put up some photos?

pv
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Old 20-07-2007, 14:09   #4
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No camera

I just bought a new hull zinc and pulled my diver's mask out of moth balls. Looks like I'm going for a swim. The old zinc is missing completely. The through hole bolt disintergrated somewhere between the zinc and the electrical connection, which I think is rather odd.

Yes, I was fortunate to schedule maintenence today, but I thought I was going to get some sailing in...... silly me..

It's a boat.
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Old 20-07-2007, 16:21   #5
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A wet zinc replacement completed despite manatee interference

Problem solved
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Old 20-07-2007, 17:12   #6
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Quote:
Originally Posted by rickm505
A wet zinc replacement completed despite manatee interference

Problem solved
A person becomes a sailor when the statement "MY GOD! THE BOAT IS SINKING!" turns into "Darn it, what is it this time. I wanted to go sailing today."
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Old 20-07-2007, 18:12   #7
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Never wanting to miss a chance to display my ignorance - you have a through hull bolt with a zinc on it? And you ground your electrical system to this? I have inspected alot of monohulls on the hard and I have never seen one of these bolts. Is it like a zinc plate or is it is it just a multihull thing?
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Old 20-07-2007, 19:56   #8
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I had a bolt dissolve that was holding the grounding plate on our starboard hull. Fortunately, the second bolt held the grounding plate on just fine. Since the bolt gradually "dissolved", I had a slow leak that I discovered before it became a small fountain.

With respect to replacing fittings in the water, I broke off a thru hull when I was in Mooloolaba, Australia. I put my finger, and then a wooden bung in the hole to stop the leak. After I assessed the situation, I decided to replace all the thru hulls on Exit Only while we were in the water since we were preparing to sail offshore. With the help of a friend, we changed ten thru hulls without a problem. As long as there are two of you, it's really not a problem as long as the thru hulls are accessible.

So if you ever have a thru hull fail, it's not the end of the world as long as you are there to stem the leak. Furthermore, you don't have to haul the boat to replace the thru hulls. I did have the boat in shallow water, just in case we encountered difficulty when changing out the thru hulls.

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Old 21-07-2007, 04:02   #9
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Not all boats have zincs. These are sacrificial anodes which protect dissimilar metals in contact with water from electrolysis. If a boat has an outboard motor, zincs aren't required as the metal is out of the water when docked. Larger boats with inboard engines all have zincs.
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Old 21-07-2007, 10:14   #10
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Wow! This sounds like a true weakest link story. We install a sacrificial anode on the hull knowing it will deteriorate and then make the attachmetnt go through the hull. Ok the bolt should not sacrifice but apparently it is doing so.

With such care taken on all the other thru hulls this seems like a bad design in some ways.

Maybe there is some maxim that says anything that goes through the hull should be removed inspected and replaced if necessary every XX years.
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Old 21-07-2007, 16:19   #11
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Quote:
Originally Posted by slomotion
I have inspected alot of monohulls on the hard and I have never seen one of these bolts. Is it like a zinc plate or is it is it just a multihull thing?
Many monohull designs incorporate hull zincs. The Taiwanese are particularly fond of doing this. Here is what is commonly used:

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Old 21-07-2007, 16:21   #12
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Quote:
Originally Posted by rickm505
I have a hull zinc, or had a hull zinc. The bolt attaching the wire inside the bilge was lying all by it's lonesum, and was no longer attached. Where it used to be attached, was a very pretty fountain of water.
There is probably no better argument for having a diver (either you or a professional) service your boat on a regular basis.
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Old 21-07-2007, 16:36   #13
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hmmm, what kind of "bolts" are you guys using? Stainless, maybe? Studs for anodes are hi-grade bronze, with bronze hardware, including backing nuts on both sides to insure the integrity of the connection to the anode. No/poor connection means no protection of anything, and the oxide coating that makes SS stainless interferes with the electrical connection. Poorly protected thru-hulls get replaced long before anybody looks at the anode stud(s).

Advice: Use hi-grade bronze studs for mounting anodes, & install with insulating sleeves, and phenolic washers and backing washers on both sides. Mount anodes with bronze washers, lockwashers and nuts.

RF Grounding plates can present a stray current problem if tied into a bonding system improperly, so often they are not, and the bolts will corrode before there's a problem with the plate.
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Old 21-07-2007, 17:56   #14
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EngNate, interesting comment. The existing zincs studs are bronze. The one I mounted yesterday came with a stainless steel bolt. It sounds like you feel this might be a problem? This is fast becoming a secondary consideration at the moment. See my other thread. I was struck by lightning today.
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Old 22-07-2007, 07:23   #15
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Yeah, I read the lightning post. Man, talk about some bad luck... Anyhow, no, don't use the SS bolt is definitely my advice, it will not provide a reliable electrical connection to the anode. Bronze hardware can be of various grades, and often chandleries and their suppliers don't even know what (grade) they're selling - it's just bronze to them. When mounting and replacing zincs, remember that electrical contact is critical. I'd advise look up an Electro-Guard dealer, EG sells stud kits with the sleeves and backing washers. You can also lookup McMaster-Carr, an industrial supply house, and get Si-Bronze all-thread and make your own.

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