I’m the first year owner of 2006 Beneteau Oceanis 393. According to the serviceman, not only is Zinc Anodes needed for the prop, but he also claims that one is needed on the keel. Since the boat is about 8 years old and I don’t see any evidence that zinc anode on the keel was ever used, is he right that one is needed, or is he trying to sell me something I don’t need? Any comments would be welcome.