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Post by roundhouse64 on Dec 6, 2013 14:53:37 GMT
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Post by Tafika II on Dec 6, 2013 15:07:20 GMT
Wow...not a pretty picture. How often do you replace your zincs? I am assuming you are in salt water. I don't know of any marina that does not have hot spots either from other boats or from underwater lines, but they all have them. We have the hull cleaned and zinc check once a month by divers for a service fee of $45...worth the investment. They change the zinc every 6-8 weeks.
How often did you have the zincs inspected and replaced?
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Post by roundhouse64 on Dec 6, 2013 15:12:10 GMT
Zincs replaced 7 months ago.
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Post by Tafika II on Dec 6, 2013 16:12:17 GMT
That seems a bit long...as I stated we change ever 6-8 weeks
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Post by MalcolmP on Dec 6, 2013 17:58:04 GMT
Strikes me that several things that might have caused this. You mention painting the sail-drive leg - what was used? if it had any copper whatsoever that might well be the source of the problem. You also mention that there is not electrolysis problems at the Marina, but stray currents do occur for all sorts of reasons and having a galvanic isolator is a sensible step. Was the boat always left plugged into the shore power? I do have a vested interest as the designer, but I do always feel reassured that I can check, and if required, replace my zinc anode within 10 minutes, without hauling out by using my Ionguard retractable and replaceable anode system www.bruntons-propellers.com/IonGuard/IonGuard_home.htmHope it gets resolved OK Malcolm
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Post by sailbleu on Dec 7, 2013 5:30:42 GMT
Are you sure no neighbour in the marina is causing this damage ? Your electrics maybe ok , but does that apply to everyone ? @ Tafika , you replace your zincs every 8 weeks Regards
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Post by MartyB on Dec 7, 2013 6:12:16 GMT
My boat lives in what is known as a HOT marina. I replace zincs every three to four months. That is TWO on the shaft. I can get maybe another month with 3 shaft zincs!
If one painted the outdrive with a copper based paint.........that could be an issue!
Marty
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Post by electricmonk on Dec 7, 2013 7:37:11 GMT
First of all I don't have a sail drive. I do have copper-coat and a galvanic isolator and my boat is attached to shore power for most of its life, at different marinas. Its now 10 years old and has been hauled out once in 2009 its next trip ashore is in January 2014. I dive under it to check anodes and in its life its had 1 large zinc and that was changed 2009 because the boat was ashore but it was still over 70% complete. I have not found any evidence of electrolytic corrosion below the waterline. IF you are getting through anodes at the rate of one every 6-8 weeks then there is something seriously wrong, I think you would be able to detect the current with a cheap multimeter! Something somewhere is bleeding milliamps to ground, it could be either the 12 volt system or the shore power AC. Start by disconnecting all the batteries then reconnect them one by one via a very sensitive ammeter - Megger is device of choice. Whatever it is that is doing it its doing it ALL the time so it will be a b8888er to find (because the panel isolators are being bi-passed - maybe) but it must be found. When you find the circuit that is discharging you then look for the actual device that is the culprit. In my humble experience you start by investigating all the non standard equipment then move on to anything with a transistor or diode - not much help in this day and age I know - sorry. edit: bilge pump switch wiring? any wire that's wet - just trying to be positive . . .
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Post by sailbleu on Dec 7, 2013 9:28:03 GMT
I never keep my AC shore power plugged in for a long time. Batteries are well maintained by solar cells Infact I rarely stay in a harbour , prefer anchoring to keep it quiet. And it's cheaper no doubt But most of the time it's someone else that causes the problem . Like electricmonk states , using a megger can do wonders for tracking down the evil, but all should be doing it of course. Regards
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Post by Deleted on Dec 7, 2013 16:33:15 GMT
We were planning to 'Coppercoat' our new SO379 - but those horror pics above are giving some concern!
Clearly there are several well documented factors that contribute to electrolysis - copper being a prime culprit. Does anyone have experience / expert advice on coppercoating the Yanmar SD20 saildrive? Will a sound epoxy barrier coating on the saildrive allow coppercoating?
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Post by Tafika II on Dec 7, 2013 17:29:56 GMT
electricmonk, I know I have a problem, but have yet to isolate it. It is now above my pay grade so I am having a marine electric's specialist check the system on the boat in my slip. I'll let you know what they find, but for now, cheap zinc are the expenditure. I do appreciate you insight and will include your writeup for the inspector. Thank you
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Post by electricmonk on Dec 7, 2013 17:37:14 GMT
Copper coating your hull wont lead to enhanced risk of electrolysis, I've put a meter on my hull hull and there is no circuit. The copper powder is suspended in epoxy, no continuity.
One of the worst cases of electrolysis I have seen (1985) was a bilge keeled boat that spent half its life dried out when the tide went out. On a swinging mooring half a mile offshore was no where near any external electrical items, had no solar or wind gen just two 100ah batteries charged by a dual output alternator. Boat left on mooring on a Sunday night having just returned from Holland, next Saturday morning no propeller blades all eaten away, propeller boss red and disintegrating. Cause traced to a 12v wire that was connected to the battery terminal to power the "car" radio, this had chaffed through and fallen into the wet bilge by the stern gland where it had been fizzing away all week. The owner asked me to investigate where his prop had gone. . . the anodes had gone, various bits of metal attached to the engine had gone . . . .
moral of the story : don't think all will be well just because your swinging on a hook.
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Post by electricmonk on Dec 7, 2013 17:49:12 GMT
electricmonk, I know I have a problem, but have yet to isolate it. It is now above my pay grade so I am having a marine electric's specialist check the system on the boat in my slip. I'll let you know what they find, but for now, cheap zinc are the expenditure. I do appreciate you insight and will include your writeup for the inspector. Thank you I think we will all be eager to learn what the solution is, sail drives and zincs have been a challenge for years but they should last a couple of seasons. Certainly most of the zincs I have replaced on sail drives are only 20 - 30% gone after a year in the sea. The old saying that McDuff get rich on all the zinc in skips has some truth in it.
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Post by sailbleu on Dec 7, 2013 20:19:15 GMT
Copper coating your hull wont lead to enhanced risk of electrolysis, I've put a meter on my hull hull and there is no circuit. The copper powder is suspended in epoxy, no continuity. One of the worst cases of electrolysis I have seen (1985) was a bilge keeled boat that spent half its life dried out when the tide went out. On a swinging mooring half a mile offshore was no where near any external electrical items, had no solar or wind gen just two 100ah batteries charged by a dual output alternator. Boat left on mooring on a Sunday night having just returned from Holland, next Saturday morning no propeller blades all eaten away, propeller boss red and disintegrating. Cause traced to a 12v wire that was connected to the battery terminal to power the "car" radio, this had chaffed through and fallen into the wet bilge by the stern gland where it had been fizzing away all week. The owner asked me to investigate where his prop had gone. . . the anodes had gone, various bits of metal attached to the engine had gone . . . . moral of the story : don't think all will be well just because your swinging on a hook. Excuse me ,....... are you talking about just 1 week to get the prop to disappear ?? Regards
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Post by electricmonk on Dec 7, 2013 20:39:12 GMT
Yes one week and the boat was on a tidal drying mooring in the Thames Estuary.
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Post by Deleted on Dec 8, 2013 10:11:53 GMT
" electricmonk" said: Copper coating your hull wont lead to enhanced risk of electrolysis, I've put a meter on my hull and there is no circuit. The copper powder is suspended in epoxy, no continuity. Thanks "electricmonk" - your advice is reassuringly confirmed by following copied from 'Coppercoat' website: <<FAQ - Does Coppercoat™ cause any problems with regards to electrolytic/galvanic action? No. With the resin carrier insulating each copper sphere, the final coating is inert and non-conductive. A current can not pass through Coppercoat™ and this coating does not cause or promote electrolysis or cathodic decay. Consequently Coppercoat™ can be safely applied to metal structures such as iron keels and steel or aluminium craft (after the application of an appropriate epoxy primer). The property of electrical non-conduction in metallic powders including copper was first discovered in 1890 by Eduard Branley and is known as the “Branley Effect”. Sacrificial anodes should be fitted in the usual manner. FAQ - Can Coppercoat™ be applied safely to boats with outboard motors or stern-drives? Yes. Applying Coppercoat™ to the hull of a boat will have no effect to an outboard motor or stern-drive. As mentioned in the answer to the previous question Coppercoat™ does not cause or promote galvanic corrosion.>>
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Post by MalcolmP on Dec 8, 2013 17:18:41 GMT
" electricmonk" said: Copper coating your hull wont lead to enhanced risk of electrolysis, I've put a meter on my hull and there is no circuit. The copper powder is suspended in epoxy, no continuity. Thanks "electricmonk" - your advice is reassuringly confirmed by following copied from 'Coppercoat' website: <<FAQ - Does Coppercoat™ cause any problems with regards to electrolytic/galvanic action? No. With the resin carrier insulating each copper sphere, the final coating is inert and non-conductive. A current can not pass through Coppercoat™ and this coating does not cause or promote electrolysis or cathodic decay. Consequently Coppercoat™ can be safely applied to metal structures such as iron keels and steel or aluminium craft (after the application of an appropriate epoxy primer). The property of electrical non-conduction in metallic powders including copper was first discovered in 1890 by Eduard Branley and is known as the “Branley Effect”. Sacrificial anodes should be fitted in the usual manner. FAQ - Can Coppercoat™ be applied safely to boats with outboard motors or stern-drives? Yes. Applying Coppercoat™ to the hull of a boat will have no effect to an outboard motor or stern-drive. As mentioned in the answer to the previous question Coppercoat™ does not cause or promote galvanic corrosion.>> Yes I would agree with that we have had coppercoat on since first launch 2008 and only have normal anode wear etc. Off topic but make sure the guys who put on the coppercoat know what they are doing, it has to be put on in very thin multiple layers or the weight of the copper will make curtain sags. Ours is now OK but the first time they did it they made a real mess...
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