Anodes - advice please



I wonder if there is anyone out there that can give me some advice? I have recently bought a 23ft sloop. She has a Dolphin petrol engine and uses 24v to start and then reverts to a 12v system. All the electirics (usual stuff) are powered by the two batteries. I beached her recently only to find that no anode has been fitted. I have been told that this is not a problem as the electrics are not bonded to an earth.

All this is gobbledy gook to me. I was under the impression that boats needed an anode otherwise their metalwork would disintigrate!

So the question is; should I be worried? If so what should I do!

Thanks - all comments gratefully recieved

Joe Simpson


As you have been told, that your electric are not bonbed to earth, this is not a proper answer. WHAT if the isolation breaks down, or you're near another vessel with an electrical leak. The prop shaft should have an anode on it. Also it's not just an electrical problem, there is galvanic action aswell. Any metal in water has its only electric current. Put any 2 different metals in that enviroment and you create a battery. An anode is the weakest metal and absorbes the effect. That why they are called sacrafical anodes.
If in any doubt what to do read Nigel calders book Called boat owners mechanical and electrical hand book, or any only books covering anodes and bonding


Well-known member
16 May 2001
France, sailing Aegean Sea.
It sounds as though this is quite an old boat? When you inspected the hull, did you notice any corrosion problems? If not, I would do nothing, especially if the boat is wooden.

Areas of concern are where galvanically active metals are in contact with more passive ones, like bronze propellers on stainless steel shafts, and especially any light metals like aluminium outdrives and the like. Steel corrodes readily in seawater and needs to be protected.

Unless you have a steel rudder or pintles, the only anodes you need are the one inside a raw-water cooled engine and, probably, a shaft anode. By fitting any others you are probably deluding yourself and you could be doing considerable harm.