Gel-Coat & Paints:
Color Matching to Your Boat, Bottom Paint, Non-Skid, Spot Repairs & Gel-Coat Spraying.
Most cracks found on fiberglass boats are gel coat cracks commonly known as crazing. They can appear as a single line, a series of parallel lines, or a spider web originating at the center of an impact. It is caused by an impact or stress with enough force to crack the surface, but not the glass beneath. The gel coat forming the finish surface is pigmented resin about 15 thousands thick. Since there is no glass reinforcement in this surface, it is more susceptible to crazing than the fiberglass under it.
It is not necessary to repair crazing, except for appearance. To make a repair, the cracked gel coat is ground away down to the fiberglass and filled with gel coat which is then sanded flush and polished. In the case of multiple crazing it may be easier to grind off the gel coat in the entire crazed area and re-spray a new layer of gel coat. The area is then sanded flush and polished. Scratches and gouges can also be repaired with gel coat by filling the area, sanding flush, and polishing.
If the fiberglass under the gel coat is cracked, the gel coat will have a wide separation as opposed to a hairline crack. The gel coat should be ground off with sandpaper to expose the fiberglass. If the fiberglass appears dark, it is sound. Any glass that appears white is damaged and must be removed. The depression or hole is filled with new fiberglass and gel coated. This should be done by an experienced repair shop.