Check the picture and make your own decision. Its easy to see that the top anode that came off a boat, protecting two marine diesels, has done sterling work.
After six years service the old anode as lost around 1 kgs of its cast weight, or to put it another way, fifty percent of its metal.
Do yourself a service, spend money on real ZINC anodes (not alloy) and save yourself lots
on engine maintainance!
How easy can this get?
Roy