How To Clean Fiberglass Boat Decks To Restore It’s Shine

Fiberglass is an excellent material for building recreational boats, but it is susceptible to wear and tear that dulls the shine. Fiberglass can become cloudy from exposure to the elements, so knowing how to clean a boat deck to maintain this material’s finish is essential. If the gel coat surface on the fiberglass deteriorates too much, it will make it easier for stubborn stains to set in. 

Cleaning your boat can be a labor-intensive task, but it's well worth it to keep your vessel looking shiny and new, protecting its resale value. Here are the steps to follow to clean boat decks made of fiberglass.

1. Vacuum and Sweep

The first step is relatively straightforward. As the gel coat on a fiberglass deck deteriorates over time, it can leave behind a chalky residue and dust. Simply sweep all the dust and debris up and vacuum it out, giving you a clear surface to work with.

2. Use a Solution to Scrub

You will want to use a specialized boat cleaning soap for scrubbing the deck. Use warm, fresh water (not salt water) mixed with a cleaning solution. Mix warm water in a 5-gallon bucket with two cups of white vinegar if you prefer a non-chemical option. A long-handled soft brush or sponge is best for scrubbing your boat. Use a specialty mildew stain remover on those spots if you have any mildew stains.

3. Rinse and Dry

Again, use fresh water to rinse the cleaning solution off your deck thoroughly. You may be trying to stave off saltwater damage with all this work, depending on where you live. It might be convenient to spray things off with a saltwater hose when you're out on the ocean, but the purpose of this job is to maintain your boat's appearance and gel coat long-term. Use towels to mop up any remaining wet spots. If you leave moisture pooling anywhere in the boat, it's likely to create more mildew.

4. Degrease if Necessary

This next step is lengthy, but it's only necessary if the gel coat on the fiberglass has started to deteriorate. If it feels pitted or porous, it's time to take the steps to restore the gel coat. If it is still in good shape, you can skip this step and finish with polishing.

You will want to use a non-scratching, degreasing boat solution for this. Use a damp cloth to apply the degreaser over the entire fiberglass deck surface. A degreaser fills in any tiny, porous holes in the fiberglass. You should then rub the excess degreaser off with a microfiber towel. Another alternative is to use a spray-on degreaser that can be rinsed off with fresh water after it's applied. Allow the degreaser to dry before moving on to polishing.

5. Polish

If you want to restore that like-new sparkle to your fiberglass deck, you must polish it. A high-gloss polish is just the thing for making your boat shine again, although this step takes some work.

If you have a smaller boat, apply the polish to a soft cloth and then rub it into the gel coat in circular motions. You may want to buy or rent an electric circular buffer if you have a larger boat. Set it to a low speed and then apply compounding and buffing pads. Polish the gel coat entirely, then wipe the boat down again with a microfiber cloth.

Fiberglass that has become too pitted or oxidized may require an additional step. Degreasing and polishing may not be enough to restore the gel coat in all cases. For more severe deterioration, you will want to purchase a specifically formulated fiberglass rubbing compound. Apply the rubbing compound by hand with a towel or with a circular buffer. If you use a circular buffer, use gentle pressure and keep it moving at all times. Your goal is to apply the rubbing compound and not scrape off the additional gel coat. Allow the rubbing compound to completely dry and set in before waxing.

6. Wax

The gel coat protects your fiberglass from the elements, and wax protects the gel coat. It also gives your boat that new-looking “shine” when it's on the water. Sun and water damage can degrade your gel coat, so it makes sense to wax your boat for that extra layer of protection.

Follow the instructions for the brand of wax that you're using and apply it evenly over the entire surface. This can usually be done with a soft cloth or an electric buffer. Cover the entire fiberglass surface and then wait for it to dry. Once dry, use a soft cloth to wipe off any excess. Your fiberglass deck should be sparkling like new after this process.