Aluminum Anodes

Ben Lee from Three Sheets Northwest has written a blog on why Aluminum Anodes are better than Zinc Anodes. He summerises  by saying... "Plus, aluminum weighs about half as much as zinc, helping with fuel efficiency as well as your back when pulling out your spares box. Just be aware that aluminum anodes corrode differently than zincs. Instead of the even pitted appearance of corroding zinc anodes, aluminum anodes tend to corrode in bigger chunks. Though it might look odd, the anode is working and should last even longer than your traditional zincs."
They are also meant to be more environmentally friendly and can be used in all water types.
Hop on over to the Three Sheets NorthWest site to read the whole article. Seems to make some sense to me; I would give it a try, but it would mean mixing anode types. A definite no-no!

 I have these zincs on my shaft and want to retain them. You can read about the line cutter anodes here.
Don’t Mix Anode Types. If you install different anode materials like zinc and aluminum, the more active anode (aluminum) will spend part of its effort protecting the less active metal (zinc). This will reduce the overall protection that you are getting. A classic mistake is adding a zinc transom anode to a Sterndrive equipped with aluminum anodes. Transom anodes are connected through the bonding system so make sure you install aluminum replacements.  

And here is a nice PDF article which helps explain it more.