Anode and prop

[cagey]

Lifted out yesterday after nearly a year, Hull anode as clean as when it was fitted last year, largish rust blisters on keel.
Shaft anode vanished and minor pitting and cratering on prop blades. shaft cross bonded at coupling , engine, keel all bonded to anode.
Skin fittings never been bonded.
Never seen electrolytic action like this before on prop.
Anyone any ideas what's going on and what to do before relaunch in 3 weeks time.
Should I bond skin fittings.
Should I make bonding into a ring at the moment its Anode - Engine Block - Keel
Should I check if engine Is also Neg grounding for batts some elec work was done in France last year whilst she was on charter
Just a bit worried (Lot)
Thanks
Keith

 

[GrahamM376]

If the main anode still looks like new and it's zinc, it would appear it's not connected and the way the shaft anode has disappeared would back this up so, I would check for continuity. Engine block should be connected to anode so check that wire wasn't disconnected when work carried out in France. I don't believe in bonding keels (others may disagree) as many I've seen bonded have more rust than unbonded. Skin fittings (except for some fridge units) shouldn't be bonded as they are already electrically isolated by plastic hose.

 

[Tranona]

No value in bonding to keel or engine as there is nothing to protect there. Hull anode may well be attached to the gearbox casing or bell housing to link to the shaft, so it needs the wire across the coupling if it is a flexible one. The fact that the shaft anode has gone suggests it has done its work - it will go before the hull one because it is closer to the prop. The hull anode needs to be in sight of the prop. If it is not eroding when the shaft anode has gone then it is not working - either not connected correctly or not in sight of prop. No need to bond to through hulls. The keel is either cast iron so no dissimilar metals to set up any galvanic action.