As long as you are going to keep the boat off of the ground you are already doing something for storing your boat. Why not go the extra step and make a cover?

A cover made from a tarp will last one season, and cost about $10. For about $30 you can get 3 sheets of 7/16 or 1/2 inch OSB, or CD exterior plywood, and some mis-tinted exterior paint and make a lean-to structure for covering the boat which will last for many years, and not blow away. Hinge this to the side of your house or garage.

Or, use 4x4 posts to make a rack, and roof it with the OSB or plywood. Two of three coats of paint should eliminate the need for shingles on the "roof" of this open air structure.

PGJ