A quick peek on your preferred search site instantly proves the questions experienced by the average boater who is attempting to match the gelcoat painted surface on their fiberglass boat. Likely the typical befuddlement can be posited as: "Why don’t boat manufacturersWhy don’t someone provide touch-up paint products for their boats like car manufacturers do?" Whether you need to mend a scratch on the hull, or are planning a do-it-yourself repainting, there are a few considerations and some helpful advise about how to approach this work.
Should I use Paint or Gelcoat?
Another common question on the boating forums is whether to paint, or re-apply gelcoat to a dull finish in order to get optimal results. Gelcoat is a polyester or epoxy resin that is applied at the time of production, and is therefore well-suited for marine conditions. Gelcoat is used on all fiberglass hulls at the time of manufacture, because gelcoat (by definition) includes the necessary mold-release agent that allows the molded hull to be extracted from the mold. You can achieve a similar glossy finish in most instances with a high-quality paint, the right sprayer equipment, and good application technique. It is perfectly acceptable to use paint on a fiberglass boat hull, and the results can be just as good. In fact, one of the most reputable yacht makers, Hatteras, now paints their fiberglass hulls, which says a lot for the debate about the superiority of gelcoat or paint, I think.
Some products like Interlux Topside or Awlgrip paints look nearly as shiny as gelcoat when dried and are easier to work with than gelcoat (which requires a lot of sanding). If you insist on maintaining the gelcoat original finish, you can avoid sanding and buffing normally required, by using a spray on gelcoat product such as Duratec. Note that even Duratec may require some sanding if the product is not correctly applied.
One-Part Paints versus A-B Paints.
There are preferred one-part paints that can be applied with a foam roller and still present a smooth glossy sprayed look to the finish of your boat. However, if you are very particular about it, you will prefer a pricier option, a two-part paint product such as those by Awlgrip or Imron, which are best applied by professional painters. You may roll or spray these types of paints with good results.
For painting the boat with a marine paint, it is highly advisable to roughen the gelcoat surface first to give the surface some tooth. Wipe the boat down with a rag of denatured alcohol and you’ll have the right surface prepared for applying paint.
Health Hazard Considerations
These paints are extremely hazardous. Always read the material safety iinstructions strictly, and use the proper breathing filters and other recommended safety gear. Also a point of consideration, the hardness of resins is well-documented and bonds well and is a great solution--especially for parts of the fiberglass hull beneath the waterline. A weakness of resin, on the other hand, is that once applied, you the polyester gelcoat options are no longer available to you. Once you use epoxy-based paints, you are, well, painted in a corner, and would need to remove everything down to the fiberglass to switch to another option.