Re: Zinc anodes...
Don't know about fresh water (I'm salt), but if in the water like mine (12 weeks), they will oxidize in air, form a white coating, and not work as well.
When I pull my big boat (VP280..2 easy off zincs), I yank them, and stick them in a covered coffee can fulla water. Also do it yearly anyway, as to whip the corrosion/frozen/twisted off bolt thing.