Wash the cracked area with dishwashing soap and water. If the cracked surface is oxidized, apply a rubbing compound to the area with a rag. Remove any wax or grease on the area surrounding the cracks using a fiberglass cleaner and rags.
Use 100-grit sandpaper to sand the area. This allows the paint to adhere better to the surface of the boat. Wipe down the area with a damp rag to remove any loose particles.
Once the area is completely cleaned and dry, apply masking tape to the edges of the area you want to paint. Paint a layer of primer over the cracked area.
Allow the primer to dry for at least two hours, and then apply a second coat of primer. Wait at least 12 hours before painting the area.
Using a roller, apply a layer of plastic-based paint in a color that matches the boat. Allow the first coat to dry for three hours. Apply a second or third coat if needed to completely fill the cracks.
Remove the tape after the last layer of paint is dry to the touch. Allow the boat to dry for at least 24 hours before placing anything on the painted surface.
