I should have said alloy not aluminium, as it is a mixture of metals, however, if you look at new outboard motors they tend to have alloy anodes.
My problem was each year at lift out my zinc anode was completely calcified so I spoke to a freind in the marine industry (a metallurgist ) and he suggested the change. Not only does if appear to work better it's half the price of Zinc.
As you point out magnesium is the freashwater choice, but if you are going in a mixture of waters multiple fixed anodes of differing metals are not practical.
Point 2, you noticed the prop anode had worn away, yes but for a Volvo folding prop, 3 years life is very acceptable, ask around!! Is it all down to the alloy anode, or the painting around the fixing holes on the prop anodes to stop them flying off, probably some of each. Do I see any sign of corrosion to prop, or leg, none I can detect after a very intensive inspection.
What I am offering the forum is my fix, sailing in salt, brackish, and freash waters, how many of you keep your boat in an estuary, brackish water?
New prop anodes painted and ready to go on
Hope this helps.
Odysseus bav 38
