Anodes overboard

[lindsay]

In the mediterranean port where i aim to spend the winter, where the water is reputed to be particularly destructive for anodes, several people have recommended "tying together several old anodes and tossing them overboard, after securing to an earth, ie the engine", if i wish to leave the boat for a couple months or so.

Details, however, are hard to come by, as is often the case.

Is this feasible and what is the best way to secure them and ensure the right contact? I have picked up a few old anodes from the yard's rubbish.

Clearly, i would need a fool proof method of remind my failing memory not to cast off with the system attached, but that is the easy part.

Thanks

 

[ccscott49]

Number one its not the water!
If the marina you are in has a reputation for destroying anodes, then it's probably an earth leak and the marina should know about it and fix it, it's not just destructive to anodes, but seacocks etc also. Hanging anodes over the side to protect your boat can be a good idea, but if they are connected to your engine they will protect, anything connected DIRECTLY to the engine. I've seen it numerous times and never heard of them doing a lot of good. But of course they may do.

 

[prv]

Hanging anodes are not an uncommon sight in marinas in the UK - often (but certainly not exclusively) on aluminium boats. The usual thing is to run a wire from the stern gear (or whatever else is being protected) up to the cockpit, ending with either a socket or a stud with a wing-nut on it. The hanging anode is then brought out of a locker when moored, the wire plugged in or clamped in place, and the anode lowered over the side. You can buy them ready-made with the wire cast into the zinc; with your old anodes it should work just as well provided you can make a good connection between the zinc and the wire. I guess either very tight clamping or some kind of soldering/brazing/locally-recasting the zinc. Would be worth giving the outer surfaces of the anode a good clean as well if they're old cast-offs with a white coating.

Pete

 

[Cloven]

I use hanging anodes all the time, mainly because I berth in fresh water & sail in salt water.

Hull & shaft anodes are Aluminum. I then use a hanging Magnesium anode when berthed in fresh water and a hanging Zinc anode when berthed in salt water. The anodes are bolted to a wire that is attached to a through bolt on the transom. Internally this bolt is then connected to the internal hull anode fitting which in turn is connected to the engine block etc. I check continuity between the anode & the internal fitting regularly.

The boat stays in the (fresh) water year round apart from when I am at sea and I replace the Mg anode each year as they get very pitted. However, I then smooth them off and use them again. The MG anodes are half of the long anodes commonly used on narrowboats, but cut in half. So far, after 6 years, I am still on the first two halves of one of the MG anodes. The Zn anode is barely wasted at all. The hull & shaft anodes do get a little pitted and I replace them again about every 2 years but then I smooth off the used ones and reuse them the next time.

Hope this helps

 

[Tranona]

Important not only to ensure the hanging anode is bonded to what it is trying to protect, usually stern gear, but also to ensure that it hangs close to that item. Can be limited use with saildrives because the drive unit is so far underwater, often well forward from the transom and with a wide beam boat the anode hangs well away laterally. It also has to be bonded direct to the drive casing inside the boat. it won't do anything for the prop as that is electrically isolated from the drive.

 

[Robin]

We have one on our new Benny Oceanis 36 because otherwise there was only a prop nut anode and nowhere easy to put a hull mounted pear shaped one that we could access inside the boat to wire up. Our hanging one ( called a fish zinc over here 'cos it is fish shaped) is a proprietary item, 5lb weight and clips onto a pushpit through hull bolt which internally is wired to the engine gearbox and therefore to the shaft and prop since there is no insulated coupling. I hope it will work well but as it is usual here to have regular diver inspections and cleans so we shall see soon enough. The prop nut zinc was new when we lifted for the pre-purchase survey and was 60% wasted when we lifted for a bottom reaint 3 months later. I am a bit paranoid because when we were liveaboards on our mobo we were on a known 'hot' dock, our now smaller Fortunately is in a different slip at least 100 yards away from the hot dock so hopefully we won't we dissolving away rapidly. Actually ourliveaboard mobo zincs and there were many of them , lasted a full year just about on the 'hot' dock, maybe because we had a galvanic Isolator but we do not have one on the new sailboat. One of the local divers was nicknamed 'sparky ' after being shocked touching an aircon inlet water seacock when cleaning the hull of a motorsailer. fortunately he survived to tell the tale.

In days of old I used to hang old anodes on our mooring chain below the top swivel but it didn't seem to do much good other than maybe a placebo effect.