Hi All,
I've noticed that my 1979 C&C 40 burns through shaft anodes at the rate of one every three months. I've also noticed that I have a ground or bonding wire that is hose clamped around one of my keel bolts; and that there is a little puddle of blackish smelly watery goo coming up through the fiberglass about 2" forward of this selfsame keelbolt. ( there are a bunch of keelbolts so I don't think it's coincidence that the one with the wire is the one with the goo ) I also check the engine zincs every couple of months but they seem to be fine. Anybody else seen this black watery goo or have problems with shaft anodes breaking down really fast? Anybody have a solution?
George
Black Goo and Bonding?!
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George ( C&C 40 )
- Skilled Systems Installer
- Posts: 254
- Joined: Thu Jan 06, 2005 12:39 pm
- Location: Williamsburg, VA
-
George ( C&C 40 )
- Skilled Systems Installer
- Posts: 254
- Joined: Thu Jan 06, 2005 12:39 pm
- Location: Williamsburg, VA
Hi Bruce,
Boat is at a dock with 30 amp shorepower attached, fridge running, and a big XantrexTruCharge 40 amp charger handling the battery banks. There is also a 120 volt system with two fans running to keep things cool and fresh. The marina is a big one with lots of big boats and lots of plugged in shorepower cords.
George
Boat is at a dock with 30 amp shorepower attached, fridge running, and a big XantrexTruCharge 40 amp charger handling the battery banks. There is also a 120 volt system with two fans running to keep things cool and fresh. The marina is a big one with lots of big boats and lots of plugged in shorepower cords.
George
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Tim
- Shipwright Extraordinaire
- Posts: 5708
- Joined: Tue Apr 01, 2003 6:39 pm
- Boat Name: Glissando
- Boat Type: Pearson Triton
- Location: Whitefield, ME
- Contact:
George,
I oppose the notion of bonding metallic fittings on board for just this reason. I believe that because all your underwater metal fittings are bonded electrically (or at least your engine, shaft, and keelbolt are bonded--I'm presuming that other fittings are bonded as well), an ongoing electrical leakage situation--either on board your own boat or, more likely, elsewhere in your marina--is causing this metallic damage to your keelbolts, and eating up your zincs. Burning through zincs every month or two is indicative of a serious amount of stray current and/or galvanic action in the water around your boat. Note that, in general, boats in marinas use up zincs at exponentially higher rates than those stored on moorings or otherwise alone.
I believe in complete isolation of all metallic fittings on board. It is one of two schools of thought on the issue, and my support of isolation is based entirely on others' experiences like yours, and on my own inspections of boats, both bonded and isolated. Note that complete isolation requires installation of a non-conductive isolator (usually a Drivesaver or similar) on your propeller shaft and coupling as well.
In my opinion, when a boat experiences the sort of electrical and galvanic action that you are (again, probably because of poor electrical installations in the marina and/or neighboring boats, but possibly on your own boat as well), bonding only enhances the effects of this action, and can (and does) begin to damage remote components that might otherwise remain unaffected.
If the stray electrical current causing this is on board your boat, fix it. If it's in the marina, request that they fix it. If it's neither of the above, then it's related to the other boats in the marina, and there's little to be done about it.
I am not an electrical expert, and, frankly, know little of the ins and outs of marina electrical systems, galvanic action, and the like. To me, the theory is unimportant; what I do know is that you can reduce the collateral damage caused by this nearly unavoidable stray current if all your metal fittings are not connected together. I bet Bruce probably has some good information to share on the electrical nature of this problem (not to put you on the spot, Bruce).
Isolate. And check out that keelbolt, too.
I oppose the notion of bonding metallic fittings on board for just this reason. I believe that because all your underwater metal fittings are bonded electrically (or at least your engine, shaft, and keelbolt are bonded--I'm presuming that other fittings are bonded as well), an ongoing electrical leakage situation--either on board your own boat or, more likely, elsewhere in your marina--is causing this metallic damage to your keelbolts, and eating up your zincs. Burning through zincs every month or two is indicative of a serious amount of stray current and/or galvanic action in the water around your boat. Note that, in general, boats in marinas use up zincs at exponentially higher rates than those stored on moorings or otherwise alone.
I believe in complete isolation of all metallic fittings on board. It is one of two schools of thought on the issue, and my support of isolation is based entirely on others' experiences like yours, and on my own inspections of boats, both bonded and isolated. Note that complete isolation requires installation of a non-conductive isolator (usually a Drivesaver or similar) on your propeller shaft and coupling as well.
In my opinion, when a boat experiences the sort of electrical and galvanic action that you are (again, probably because of poor electrical installations in the marina and/or neighboring boats, but possibly on your own boat as well), bonding only enhances the effects of this action, and can (and does) begin to damage remote components that might otherwise remain unaffected.
If the stray electrical current causing this is on board your boat, fix it. If it's in the marina, request that they fix it. If it's neither of the above, then it's related to the other boats in the marina, and there's little to be done about it.
I am not an electrical expert, and, frankly, know little of the ins and outs of marina electrical systems, galvanic action, and the like. To me, the theory is unimportant; what I do know is that you can reduce the collateral damage caused by this nearly unavoidable stray current if all your metal fittings are not connected together. I bet Bruce probably has some good information to share on the electrical nature of this problem (not to put you on the spot, Bruce).
Isolate. And check out that keelbolt, too.
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George ( C&C 40 )
- Skilled Systems Installer
- Posts: 254
- Joined: Thu Jan 06, 2005 12:39 pm
- Location: Williamsburg, VA
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JetStream
- Skilled Systems Installer
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- Joined: Sat Apr 26, 2003 8:53 pm
- Boat Name: Sojourn
- Boat Type: Pearson 27
- Location: Jamestown, RI
Like Tim says, corrosion of zincs is no real mystery. There has to be a potential (voltage) difference between two pieces of metal on your boat that are connected by seawater. Current then flows from higher to lower potential and a plating cell is formed. Your sacrificial anode (zinc), or your sacrificial keel bolt (oh no!!) starts plating out. Here is a link to an article that pretty well describes what is going on: http://www.boatus.com/boattech/MarineCorrosion.htm
Marinas can be major problems. In addition to having the correct setup from the marina, you really need an isolation transformer to keep you separate from everyone else's problems. Many poorly wired marinas are just known as "hot" zones where your metals will start corroding as soon as you dock there, because of all the stray electrical currents flowing in the area. It is extremely important to find the source of the problem quickly, before your keel falls off because the bolts became sacrificial.
Marinas can be major problems. In addition to having the correct setup from the marina, you really need an isolation transformer to keep you separate from everyone else's problems. Many poorly wired marinas are just known as "hot" zones where your metals will start corroding as soon as you dock there, because of all the stray electrical currents flowing in the area. It is extremely important to find the source of the problem quickly, before your keel falls off because the bolts became sacrificial.
Bruce
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George ( C&C 40 )
- Skilled Systems Installer
- Posts: 254
- Joined: Thu Jan 06, 2005 12:39 pm
- Location: Williamsburg, VA
Hi Guys,
I just got back from the boat and found out what was going on with the keelbolt at least. The orange wire that connects to the keelbolt wasn't attached to anything. It appears someone was using it as a ground for the VHF radio at one point but then disconnected it. I completely removed the wire this afternoon. I also found the source of the black goo. At some time in the past someone had installed a couple of aluminum spacers ( like big washers ) under the lock nut of the keelbolt and then fiberglassed over the spacers. The black goo was coming from the breakdown of the aluminum that was in contact with the stainless steel of the keelbolt. The reason it was oozing up 2" in front of the keelbolt was that is where a little piece of the aluminum spacer came to the surface of the fiberglass covering. So while it was a galvanic problem it was not part of the overall galvanic issues that are affecting the shaft anode. Also, it appears that the aluminum was acting as a sacrificial zinc in this instance and the stainless steel keelbolt is in perfect shape. I'll grind out the rest of the aluminum spacers and replace with stainless steel to solve that problem.
I also checked all the through hulls on the boat and none of them are bonded. They all appear to be in excellent shape.
As it stands now I will take the advice that says don't bond anything. If I have to replace the shaft zinc every three months then I guess that's just the price of being in the marina.
Also, I'm going to now check out JetStream's article fromt he previous post and try to learn a bit more about this stuff.
Thanks again to everyone,
George
I just got back from the boat and found out what was going on with the keelbolt at least. The orange wire that connects to the keelbolt wasn't attached to anything. It appears someone was using it as a ground for the VHF radio at one point but then disconnected it. I completely removed the wire this afternoon. I also found the source of the black goo. At some time in the past someone had installed a couple of aluminum spacers ( like big washers ) under the lock nut of the keelbolt and then fiberglassed over the spacers. The black goo was coming from the breakdown of the aluminum that was in contact with the stainless steel of the keelbolt. The reason it was oozing up 2" in front of the keelbolt was that is where a little piece of the aluminum spacer came to the surface of the fiberglass covering. So while it was a galvanic problem it was not part of the overall galvanic issues that are affecting the shaft anode. Also, it appears that the aluminum was acting as a sacrificial zinc in this instance and the stainless steel keelbolt is in perfect shape. I'll grind out the rest of the aluminum spacers and replace with stainless steel to solve that problem.
I also checked all the through hulls on the boat and none of them are bonded. They all appear to be in excellent shape.
As it stands now I will take the advice that says don't bond anything. If I have to replace the shaft zinc every three months then I guess that's just the price of being in the marina.
Also, I'm going to now check out JetStream's article fromt he previous post and try to learn a bit more about this stuff.
Thanks again to everyone,
George