learning as I go since I've got this boat - earlier relied on friends in UK who knew it all re. maintenance ! - so hope you will all forgive me if I test your patience with my ignorance ! ..
Have got zinc anodes [2] on shaft to protect prop, P.bracket etc but have been told that should connect engine to a sacrificial anode as well. any ideas on how this is done..ie wire from where to where and where does the zinc go? Did have Nigel Calder's book but for some reason cannot find it, and preparing for a longish trip this Xmas new year, so keen to get evthg right.
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 You need the anode to be screwed into the top of the tank. This means it can be replaced easily, though sometimes the anodes are built into a special outlet fitting. You should be able to do it yourself as long as you have the right tread for the nut to go on to.
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thanks Sophie. Not sure tho which tank you would mean on this boat. My Fuel tank is a distance away and made of some kind of plastic [- polypropylene?] Was also told that my Yanmar GM20 should have a sacrificial anode somewhere..can't see it tho! ..but was told that there should be a further wire from the engine [block?] to another anode.. tho not sure where. [brief bar talk sometime back with a chap who's no longer here so can't check with him]
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 Hi David, have you already got any anodes bolted through your hull, you know like those big pear shaped ones???
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Hi Chas, no. Therein some of my uncertainty because I have seen these, mainly on wooden boats [I guess because of nails etc?]and know they have huge ones on steel vessels. but can't recall seeing on fyg. Should I hve one? Part of my confusion is that I thought what happened is that electrons ? leeched away from the less noble metal [leaving it degraded and brittle like orange brass] when in the same briny conductive solution as another metal. But here the engine isn't in a soup, and would you get the same procedure simply by connecting a wire, like to an earth, but here to an anode??
so all I have is a couple of zincs bolted onto the shaft. There is one curious loose wire though, screwed into the keelson under the shaft thus near the engine but not connected to anything. this may be nothint to do with anything, but it is curious. Noone I 've shown it to understands it and previous owner is in China ! or maybe now back in Yorkshire.
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Galvanic corrosion is quite a complex subject David, I don't know that much about it but it is different to oxidising or rusting and involves electrical charges rather than just chemical reaction I know that all metallic objects take up a differing electrical potential when immersed in an electrolyte (seawater). The more noble the metal, the higher the potential. If a piece of zinc and a piece of stainless are immersed in seawater electrons will try to flow from the zinc to the stainless, they will probably never get to the stainless but they have left the zinc.
I wouldn't worry about bonding your block at the moment but when you next have the boat out, it may be worth fitting an anode then and it may be worth while connecting the wire from the keelson to it.
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 Trying to get you a quick answer but our guru is proving elusive - reindeer interference probably, bad at this time of the year. Best immediate solution, throw the problem at your local chandler who should know. Good luck.
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thanks Peter. unfortunately no local chandler here! or even reindeer, tho plenty of camels and the odd white elephant. but I think / hope chas is right - cannot quite understand how the engine would be affected [except of course by ordinary rust] since it isn't in an electrolytic solution.. must find that Nigel Calder book.
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That's correct David but as I said it may be worthwhile fitting an anode and connecting your keelson to it when it is convenient, probably no desperate rush.
I wouldn't trust any chandler I know to add up correctly so Peter must know an exceptional one.
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Yeah David, be careful. All I know about this electrolysis stuff is I had a swimming pool once with a sacrificial anode in the purification system. The supplier sent me a replacement anode every month because the previous one was eaten away to nothing. Sea water, electricity and your prop shaft could make a nice meal.
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Warning well taken, Peter.hope the shaft, P-bracket and prop are protected by the 2 zincs on shaft..tho must check how these are after 3 months, last time I put one on, it was gone when I checked 6 months later.. the thing tht puzzled me is whether one needs to protect the engine as well and if so how. feeling reassured by Chas' comments. Wish I'd paid attention 35 years back in chemistry class..or is it physics? [shows how much I know!]
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It doesn't matter how quick the anodes disappear, just make sure you replace them before they have completely gone.
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 Hi David, just picked up your query on anodes. From my experience, and how the pros did it for me was thus; anode was bolted to the outside of the hull with stainless bolts, then wires led from the engine and gearbox (one each) to the ss bolts inside the hull and secured under the nuts. I carried on board my boat the prop that was fitted previous to this system and it was like a lace curtain with erosion. The system was fitted when I bought the boat and after fifteen years there was not the slightest sign of deterioration on the prop. So it must have been correct. Regards, Harry. PS. I also had round anode bolted through the base of the skeg...connected to nothing, but it seemed to attract electrolysis for it gradually used to waste away, very gradually.
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David, go to Google and get a Yanmar owners manual. Most engins have a zink attatched to the inside of the cooling system. The owners manual will tell you where it is and how to change it. Or check with your Yanmar dealer. Now I have a question for the gang. I have replaced all my thru-hulls and sea cocks and want to know the best way to ground them or is it necessary to do so. I am planning on using an over the side fish-zink at the dock. Bonding all the thru-hulls to it with boat wire and a wiper in the shaft. Comments please.
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 | TMS Poloshirt winner |
30/11/07 16:51
 Hi Charles your answers could be here....... If you missed the articles in PBO on 'Electrics Afloat', then you might consider the book of the same name, by Alastair Garrod from Adlard Coles, in association with PBO.It was reprinted in 2005 from its original form in 2002. It won't solve your electrical problems overnight but it will possibly give a far better understanding of all the electrical information that most boat owners may ever need. e.g.:- Basic electrics theory. Anodes/Electolysis/grounding. Marina/Shorepower/a.c.safety-distribution. D.C. distribution. How to wire in all those extra bits such as wind generators, solar panels, plotters,AIS,Etc. Even if you don't have the wherewithall to do the jobs yourself it will probably leave you far more knowledgeable and able to discuss problems with those who can. It comes in A4 format, with highly coloured diagrams/pictures with extremely good information to accompany, and doesn't talk to you as if you already had a 'Btech' in electrical engineering. It is similar to that which you would expect to find in the better GCSE and 'A' level text books today. Of all the boat electrical books I have perused, this comes out as one of the best. It retails for less than £20, far less on some websites, but make sure you get the latest print.
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| Edited: 30/11/07 16:52 |
Ok Scotty I will look for the book. How ever I'm in California so it might be diffacult to locate. Thanks.
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| TMS Poloshirt winner |
01/12/07 00:08
 Amazon-co.uk or .com-you can source books from anywhere-and postage airmail usually about £2.50/$5-if dot com doesnt have it over there you check dot co dot uk-who probably will Phil
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| TMS Poloshirt winner |
02/12/07 23:21
Hi Charles Phil beat me to it. The only additional info may be the ISBN of the book ISBN 0-7136-6149-6 which should enable you to easily order this book in the U.S. from any website or bookshop Some voltages may vary as far as shore supply in the U.S. are concerned , but overall the theories all 'stand up' I'm sure other books were mentioned recently on boat electrics on this site, where Cathy and others had some suggestions, but I havn't had time to trawl thro the threads and blogs. Scotty.
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Okay I've ordered the book from the UK. Not available here in the US. Thanks.
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