Cruising at high speeds on the waters of the ocean or a river is a thrill that speedboat owners live for. Owning a speed boat and knowing how to handle it carefully and safely is an important step in experiencing those thrills, but you don't want your speedster image tarnished by a dull paint finish on your craft. Whether the colour is all wrong or the surface features damage and scars, you can repaint a fibreglass speedboat yourself with the proper preparation and material choice.
Don a dust mask, safety goggles and protective suit when dealing with your fibreglass boat. You will be sanding the fibreglass, which will produce a lot of dust and sand that can irritate skin, eyes, throat and lungs if breathed in.
Soak a 220-grit wet/dry sandpaper pad for an orbital sander in cold water for 10 minutes. Attach the pad to an orbital sander and sand the entire surface of the boat evenly. Stop as needed to re-moisten the sandpaper or replace a worn pad. This sanding removes the old finish to make way for the new paint.
Fill in any scratches, chips or damage on your boat with epoxy-based fibreglass filler putty and a putty knife. Force the putty into the damaged areas so that they are flush with the surrounding surface. Scrape away all excess with the putty knife. Allow the filler putty to dry overnight before continuing.
Sand the surface again using the same procedure as before to ensure that all repair work is flush with the surrounding boat and that the surface is thoroughly roughed-up for the paint.
Wipe down the entire surface with a rag dampened in white spirit to remove surface sanding dust, dirt, grease and other contaminants. Any contaminants remaining on the surface will mar the bond between the paint and the boat.
Rinse the cleaned area with fresh water from a hose or on a sponge to remove residual white spirit. Allow the surface to dry fully before continuing.
Coat the fibreglass speedboat with a layer of silicone-based primer. The primer will fill in the porous areas of the fibreglass, ensuring a smooth, even coat of final paint on the surface. Work in smooth strokes across the surface with a paintbrush, overlapping lines of paint by ½-inch. Allow the primer to dry fully before continuing.
Sand the primer coat lightly with the 320-grit wet/dry sandpaper to ensure that it is rough and ready for the paint application. Make only one pass with the sander, since you don't want to remove the primer. Wipe off all sanding dust with a tack cloth.
Top the primer with silicone-based fibreglass paint, using a paintbrush. This paint is very thick, so put only a little on your brush at a time to avoid drips and uneven areas. Coat the entire fibreglass surface in one coat and allow it to dry (generally between 16 and 24 hours) before continuing.
Sand the first coat with 320-grit wet/dry sandpaper and apply a second coat using the same methods. Allow this final coat to dry for at least 24 hours before exposing the boat to any moisture.
Find all materials for this project at marine-supply shops. If at any time you are unsure of your ability to finish this project without damaging the boat, contact a professional for help. If you are painting your speedboat outdoors, do so on an overcast day with little wind and low humidity. Direct sunlight, high winds and high temperatures and humidity will change the drying times of the primer and paint, resulting in streaking or spotting. If you have trouble with brush marks in your paint, dampen just the tip of a clean brush in a little paint and swipe slowly across the surface front-to-back with the brush. The small extra bit of paint will fill in brushstrokes.