Back to the topic:

If there is room between the propeller and the strut, put a donut zinc on the
shaft between the two. Nothing grows on the zinc, of course, since it is
constantly depleting. But it also seems to extend a zone of protection that
prevents or greatly reduces growth within a few inches of the zinc. That's
enough to keep the prop hub clean, which is where maximum growth occurs. A
frequently used prop won't have much growth beyond the hub in any case.