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Old 03-16-2019, 12:00 AM   #21
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I am a fan of electro-guard. While they are not necessary on a fiberglass boat they can alert you to stray current issues.
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Old 03-16-2019, 02:45 AM   #22
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As has been said, bonding causes divisions amonmgst owners.

On our Fleming, everything is bonded, and bonded well. 2 main ship's anodes connect to everything. Shafts have zincs as do the stabilisers, bow and stern thrusters, engines, generators and the sea-water stabilser oil coolers.

The key for us is every year to ensure that all connections are well made and that nowhere is the impedence greater than 0.3 ohms between the main zincs and the item being bonded.

In 16 years, no problems. Yo my knowledge, all Flemings are done this way
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Old 03-16-2019, 10:46 AM   #23
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I never worried about it till I got my steel hulled BR 44. Then I read everything I could find. No one agreed. It turned out the steel boat almost sank when a guy in the next slip dropped an AC line in the water and left it there for a week. His boat DID sink in the slip. Mine was protected by the issolation transformer, but the bronze back plate on the heat exchanger turned to dust and would have sunk the boat except that I was onboard when it failed. I now, no longer use shore power....ever..... On my MS 34 Mk1, from what I can see, nothing is bonded.. BUT, the diver says my zincs are in great condition so I wont be touching anything for now.
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Old 03-17-2019, 08:09 AM   #24
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Originally Posted by greatpapabear View Post
As has been said, bonding causes divisions amonmgst owners.

On our Fleming, everything is bonded, and bonded well. 2 main ship's anodes connect to everything. Shafts have zincs as do the stabilisers, bow and stern thrusters, engines, generators and the sea-water stabilser oil coolers.

The key for us is every year to ensure that all connections are well made and that nowhere is the impedence greater than 0.3 ohms between the main zincs and the item being bonded.

In 16 years, no problems. Yo my knowledge, all Flemings are done this way
Fleming does do a good job of bonding, and the standard you are holding them to is very lofty indeed, the acceptable resistance between anode and protected metal is 1 ohm. Your regular inspections are applauded, too few owners pay attention to bonding system maintenance.

One change Fleming has made at my request in the past few years is the means by which bonding wire ring terminals are connected to the copper bonding bus, they used to use tapping screws (these are prohibited by ABYC guidelines for electrical connections, bonding and otherwise), in the last couple of years they switched to machine screws.

Many, the majority of, boat builders use tapping screws for bonding connections, it nearly always results in high resistance because the connection loosens over time. These connections should be checked regularly, and where they can't be tightened, a bus bar, or at the very least a through bolt, installed in their place. The bonding article I shared earlier covers this subject.
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Old 03-17-2019, 08:24 AM   #25
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Quote:
Originally Posted by Steve DAntonio View Post
Fleming does do a good job of bonding, and the standard you are holding them to is very lofty indeed, the acceptable resistance between anode and protected metal is 1 ohm. Your regular inspections are applauded, too few owners pay attention to bonding system maintenance.

One change Fleming has made at my request in the past few years is the means by which bonding wire ring terminals are connected to the copper bonding bus, they used to use tapping screws (these are prohibited by ABYC guidelines for electrical connections, bonding and otherwise), in the last couple of years they switched to machine screws.

Many, the majority of, boat builders use tapping screws for bonding connections, it nearly always results in high resistance because the connection loosens over time. These connections should be checked regularly, and where they can't be tightened, a bus bar, or at the very least a through bolt, installed in their place. The bonding article I shared earlier covers this subject.
Hi Steve, thank you. You are so right about the self tapping screws. I've changed so many after finding they'd become loose or corroded, I've lost count. I've also found some 'flexible' earthing wires to be only a few cores and therefore inflexible when used on moving parts such as the rudder bar.

However, it's all in a day's maintenance. Mind you, I say that, but a full engine (2 x main & 2 x generator) and general service takes me a good 8 days. leaving many aches and pains which take the rest of the year to get over!
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Old 03-17-2019, 08:35 AM   #26
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I never worried about it till I got my steel hulled BR 44. Then I read everything I could find. No one agreed. It turned out the steel boat almost sank when a guy in the next slip dropped an AC line in the water and left it there for a week. His boat DID sink in the slip. Mine was protected by the issolation transformer, but the bronze back plate on the heat exchanger turned to dust and would have sunk the boat except that I was onboard when it failed. I now, no longer use shore power....ever..... On my MS 34 Mk1, from what I can see, nothing is bonded.. BUT, the diver says my zincs are in great condition so I wont be touching anything for now.
I'm an advocate of isolation transformers (especially on metal boats but all hulls benefit), they are invaluable for a variety of reasons, detailed here http://stevedmarineconsulting.com/wp...ansformers.pdf

While I don't doubt what you experienced, it's worth pointing out that the incidence of AC (shore power) induced corrosion is extremely low, and when it does occur it usually is harmful primarily to aluminum (hulls, and stern drives typically). Stray AC leakage is very common in marinas, it's why you shouldn't swim there, but it's not a corrosion risk per se.

Also, stray AC (or DC for that matter) current outside your boat, especially a steel hull, almost never causes corrosion on an internal component like a heat exchanger, because they are considered to be in 'different bodies of water', the current will not travel past the steel hull, up a long, narrow hose and to the heat exchanger. Also, if you had properly wired isolation transformer, the circuit between the boat with the leaky shore power and your heat exchanger could not be completed in any event. This is also why the pencil anodes in a heat changer don't protect your prop and shaft, and why running gear and hull anodes don't protect heat exchangers, they are in different bodies of water.

Again, I don't doubt you experienced these failures, but I do question the claimed means by which they occurred.

This article details the two most common types of corrosion, explaining how they occur https://stevedmarineconsulting.com/u...osion-mystery/

This one covers aluminum specifically https://stevedmarineconsulting.com/u...num-corrosion/
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Old 03-17-2019, 05:35 PM   #27
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I'm an advocate of isolation transformers (especially on metal boats but all ,,,,


Me too. Plus, any xfmr i buy will have a 208v primary tap.
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Old 03-18-2019, 08:54 AM   #28
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BTW, if your zincs last too long, something is probably wrong, they should erode. If they aren't eroding (they are actually corroding), or if they are getting marine growth on them, they probably are not connected to the bonding system, or underwater hardware, properly, with a low resistance connection. Again, one ohm is the maximum allowable resistance between anode and protected metal.
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Old 02-02-2021, 10:34 PM   #29
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Does a grounding plate perform the same function as a transom zinc?
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Old 02-02-2021, 11:26 PM   #30
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Does a grounding plate perform the same function as a transom zinc?
No. It is not sacrificial.
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Old 02-03-2021, 12:01 AM   #31
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Ground plane or plate could be for a radio or maybe lightning protection. Your anodes are for corrosion control.
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