Hull Anode bonding - acceptable resistance?

[neil1967]

I have a prop (maxprop), shaft and hull anode on my glass fibre yacht. When I lifted her this year, after some 18 months, the maxprop anode was about 50% consumed, the shaft anode about 80% and the hull anode about 10-20%. The hull anode is connected via a heavy gauge wire to a bolt on the stern tube. I checked the resistance between the anode and the propshaft and found it to be 40 ohms. On closer inspection the resistance is actually between the bolt on the stern tube and the propshaft. Does this sound about right? If not, how might I improve the connection between the propshaft and the anode?

Neil

 

[VicS]

I have a prop (maxprop), shaft and hull anode on my glass fibre yacht. When I lifted her this year, after some 18 months, the maxprop anode was about 50% consumed, the shaft anode about 80% and the hull anode about 10-20%. The hull anode is connected via a heavy gauge wire to a bolt on the stern tube. I checked the resistance between the anode and the propshaft and found it to be 40 ohms. On closer inspection the resistance is actually between the bolt on the stern tube and the propshaft.

Does this sound about right? If not, how might I improve the connection between the propshaft and the anode?

Neil

No it does not sound right at all.

Connecting the hull anode to the stern tube might protect the stern tube but there is no metal to metal contact between the stern tube and the propshaft is there? Therefore the hull anode wont protect the prop or shaft.

The resistance between the anode and what it is fitted to protect should be negligible.

Normally hull anodes are connected to the engine block or gearbox and any flexible coupling in the shaft bridged to complete the circuit. Alternatively to brushes running on the shaft inboard of the stern gland. (See M G Duffs "Electro Eliminator).

You may not need the hull anode if the shaft and prop anodes are is doing their job.

 

[neil1967]

OK, thanks - should be easy to remedy.

Neil