Has Gail has stated a zinc anode once launched in water and then removed from water will start to form an oxidized coating which makes it useless. I have talked to many boat owners about replacing their anodes when they switched from trailering to full time in water storage. The first response is the anodes are like new and have not eroded at all. My comment back to them is because they are not working!! When the zinc is introduced to the air it oxidizes. IMO Zinc anodes should not be used on trailerable or lift boats. Use aluminum anodes. Zinc anodes do not protect stern drives or outboard components very well either. Aluminum alloy anodes will do a much better job in protecting. Actually I believe Aluminum alloy anodes add better protection to all boats Sterndrive ,out board and inboard. I switched over after the first year of owning my Cutwater. I have never used zinc anodes on any of my outboard or stern drive boats. Mercuiser/Mercury marine will void the corrosion warranty if zinc anodes are used on their products. I don't know why Fluid motion uses Zinc anodes on trailerable boat!