How to Prime Bare Fiberglass Below the Water Line
- 1). Power wash the boat using a pressure washer to remove algae or other marine growth below the waterline.
- 2). Mix a solution a boat wash and water in a plastic bucket; refer to the label directions for the correct ratio of boat wash to water. Scrub the area below the waterline vigorously with the boat wash solution and a scrub brush, removing all remaining debris, marine growth, dirt and grease. Rinse with fresh water; allow the surface to dry.
- 3). Saturate a rag with fiberglass solvent wash. Treat a small section of the hull below the waterline with the solvent wash; before the solvent wash dries, wipe it off with another clean shop rag. Continue this process until the entire hull, below the waterline, is treated with the fiberglass solvent wash.
- 4). Mask off the area above the waterline by attaching masking paper to the hull with masking tape.
- 5). Fill the reservoir of a paint sprayer with no-sand fiberglass primer. Spray a continuous coat of primer on the area below the waterline. Allow the primer to dry. Follow the directions on the can of primer for drying times.
- 6). Clean out the paint sprayer, completing the priming of the fiberglass boat below the waterline.