The gel coat on your boat is the protective layer that covers the fiberglass. It is a clear, tough, glossy finish applied to the surface of fiberglass to protect it from damage. Continue reading to learn how to restore gelcoat on a boat.

How it Works

The exterior surface of a fiberglass boat is made of a special resin called gelcoat. The core composites of resin-saturated glass material offer physical value, but gelcoat shields the hull and provides it color and sheen. When the gelcoat is then sprayed into the hull mold, it takes on the shape and texture of the mold surface. The ultra-high sheen of most new boats is solely owing to the highly polished, mirror-like surface of the mold used in the boat’s initial manufacture. Gelcoat’s soft surface gradually erodes by age and contact, leaving it drab and chalky. However, the gloss is typically recoverable. 

How to Clean Fiberglass

The first step in reviving the sheen to the old gelcoat is always a detailed washing. Add a cup of detergent to a gallon of water — warm water is preferable — and use a sponge to clean the area with this mixture. Wear rubber gloves to keep your hands safe. If mildew is found, add a cup of household bleach to your cleaning solution. Difficult stains, such as fish blood and waterline scum, can necessitate the use of a powerful cleaning developed for fiberglass. Rinse the clean surface completely and allow it to dry.

Degrease Gel Coat 

For trustworthy results from wax or polish, the gelcoat surface must be totally clear of oil and grease. Detergents frequently fail to completely remove these pollutants from weak gelcoat. Wipe the entire surface with a rag saturated in MEK (recommended) or acetone, flipping the rag often and changing it when you run out of clean regions. Remember, use thick rubber gloves to protect your skin.

Waxing Rules 

Keeping the gelcoat covered with wax-starting when the boat is new is the greatest method to extend its life. Gelcoat that is regularly waxed can keep their sheen for 15 years and more. The primary function of a coat of wax is to protect the gelcoat. Application directions vary by manufacturer, but in general, you spread the wax in a clockwise direction with a cloth or foam pad. Allow the wax to dry to a haze before buffing away the remaining using a soft cloth, such as an old bath towel. The residual wax plugs small pitting in the gelcoat and creates a fresh, smooth, shiny surface.


Polish is an abrasive, similar to ultra-fine sandpaper. Rather than covering the pitted surface, polishing eliminates it. Sprinkle polish to a tiny area at a time using a soft cloth, rubbing in a circular pattern until the top is glossy. After polishing, add a coat of wax to preserve the top and boost the sheen. Some polishes contain wax in their formulas.

Rubbing Compound 

If the gelcoat becomes so worn that polishing it will not revive its luster, you will need to use a rubbing solution, which includes harsher abrasives. Because wax on the surface might cause the material to cut irregularly, clear all wax by “sweeping” the area in one direction — not back and forth — using rags wet with dewaxing solvent or toluene. Choose a fiberglass-specific rubbing compound and apply it in the same manner as polish, rubbing it in a circular motion until the surface becomes glassy. Because the gelcoat on your yacht is around ten times thicker than the paint on your automobile, the compound should not cut all the way through it as long as you avoid rubbing in one spot for too long. Stop when the gelcoat becomes clear. Polish the surface once it has been mixed, then treat it with wax and buff it. If your gelcoat is thick enough coating your boat will be seamless. This method will recover the sheen to fiberglass in practically any state.

Electric Buffer 

You can wax, polish, and compound by hand, but on anything larger than a small boat, your arm will grow extremely tired. An electric buffer takes most of the labor out of maintaining a yacht polished and is less costly than shoulder replacement. Electric buffers function at rather moderate rates, so don’t try to “make do” using a polishing bonnet attached to a disk sander or a sanding pad put into a drill. You will either destroy the surface or the device. A buffer with a rotational motion will leave fewer swirl marks.

Gelcoat Restoration 

A variety of solutions claiming to repair the top of the gelcoat have hit the market in recent years. Restorer compositions rejuvenate the gloss in the same manner that wax does, by producing a fresh smooth texture, but without the need for polishing.  The effects can be striking, but because restorers are a plastic (acrylic) layer, they can wear out, flake off, and possibly discolor. In conjunction with the restorer, most restorative packages contain a preliminary wash and, in some cases, a shine. A stripping tool is needed to remove old sealants. There are some changes in the suggested application, but in fact, it is the same as previously mentioned — clean, polish, and coat. Because acrylic sealer is often water-thin, it is considerably simple to apply to the hull than, for example, paste wax. It also dries to a hard coating, eliminating the need for polishing.  Therefore, you will need to apply numerous coats — five is common — to achieve a decent sheen. If the product you’ve chosen doesn’t come with an applicator, wipe the sealer onto the gelcoat using a sponge or a soft cloth. Because drying durations are short, additional coats should be applied quickly. 

Bilbo’s Marine 

Our job is not to just clean your boat and make it shine. Our job is to give your vessel the protection it needs from the harsh elements to ensure longevity. Contact Bilbo’s Marine for your next boat service today!