My Yamaha OB is always in the water, and the lower unit, including the prop, encounters a significant corrosion problem. Yes, I do have a sacrificial plate above the prop and the Ariel is used in fresh water. The prop is an aluminim alloy.

The problem of the disappearing propellor (and lower unit) is commonly recognized (The Yamaha prop is about $100, so, being cheap, I don't like to replace it annually).

I have painted the prop with TRI-Lux II which seems to work well as protection. Tempo did not work. But the prop has to be repainted each year, with a significant buildup. My motor mechanic has told me that the rough surface of the paint on the propellor is responsible for loss of thrust I have been experiencing.

The question is, what have others found best to protect the prop? Or is sanding it every year and refinishing it the only or the best solution?