Anode advice please

[argus]

On my Colvic watson 26 there is insufficient room on the shaft to add a shaft anode a rope cutter takes the available space, the rudder is supported by a steel skeg. A previous owner had mounted a large anode on a block of wood in the hollow of the skeg two bolts pass upwards through the bottom of the skeg through the wood and the anode is held by nuts and washers, to protect the propeller a copper strap is attached between the anode fixing and the stern bearing. Inside the boat the stern gland is earthed to the engine block rudder stock and bilge keels, there is a strap across the shaft coupling. I have tried to measure the ohms between new anode and shaft - it is less than 0.1, however I have found a resistance of over 50 ohms between anode and skeg presumably where the bolts pass through the skeg there has been a lot of corrosion each year I have to chip off the rust.
Can I make a second strap of copper between the anode and a new connection on the skeg without creating a battery?

Peter Richards

 

[afterpegassus]

Between the coupling and the sterngland I mounted a carbon brush from an old washing machine motor so that there was good contact with the shaft and bonded this to the through hull rods of the external anode. This was done five years ago and I have had no problems.

 

[VicS]

Are you talking about copper straps on the outside connecting with the anode? If you are then you will have a situation in which the anode is rapidly consumed.

If it is necessary to protect the prop I would fit a hull anode for that purpose with a bonding cable to the engine or gearbox and a bridging strap across the flexible coupling, but a better arrangement would be to connect it to brushes running on the shaft in board of the stern gland as Totaig suggests.

I would protect the skeg with separate anodes, one on either side, but maybe the one you describe will be adequate. The anode(s) for the skeg must be either in good electrical contact with it or the one you describe must be bonded to the fixing bolts internally.

Recommend you study the MG Duff website