Fiberglass boats are built to last, but keeping them looking sharp takes regular care. Between sun exposure, oxidation, salt, and grime, your gelcoat can quickly lose its shine if not properly maintained. The good news? With the right approach and the right marine-grade products, cleaning a fiberglass boat is fast, easy, and incredibly effective.

This guide breaks down how professionals clean fiberglass boats, step-by-step, plus the best products to use so you can keep your vessel looking new all year long.

1. Rinse the Entire Boat to Remove Salt & Surface Dirt

Always start with a strong freshwater rinse. This removes salt, dust, dried algae, and loose grit that can scratch the gelcoat when you scrub.

✔ Tip: Use a high-pressure nozzle but stay safe around seals, decals, and electrical areas.

2. Wash with a pH-Neutral Marine Soap

A proper boat wash matters. Household soaps strip wax and damage gelcoat — but a pH-balanced marine soap cleans without removing protective layers.

Look for formulas that:

• Lift dirt fast

• Are salt-neutralizing

• Are biodegradable

• Leave a slick, glossy finish

Use a soft brush for hull sides and a microfiber mitt for sensitive areas.

3. Deep-Clean Stubborn Spots

After the wash, inspect the hull. Areas that stay dull or chalky likely need targeted cleaning:

For rust or waterline stains:

Use an acid-free stain remover.

For grime stuck in non-skid areas:

Use a nonskid deck cleaner formulated for fiberglass.

For mold or mildew:

Use a marine mildew stain remover safe for gelcoat.

✔ Tip: Never use abrasive brushes or pads — they scratch fiberglass.

4. Remove Gelcoat Oxidation (If Needed)

Oxidation is the biggest enemy of every fiberglass boat. If your hull looks faded, hazy, or chalky, you’ll need a fiberglass compound or oxidation remover.

Choose the right strength:

• Light oxidation: cleaner wax

• Moderate oxidation: medium compound

• Heavy oxidation: cutting compound + rotary buffer

Work in small sections and finish with a microfiber towel for a smooth shine.

5. Apply a Protective Wax or Sealant

After cleaning and compounding, always protect the gelcoat.

You can choose between:

Traditional marine wax

• Deep glossy shine

• 4–8 weeks of protection

Polymer sealants

• Longer durability (2–4 months)

• Excellent UV protection

Ceramic coating sprays (2025–2026 trend)

• Extreme hydrophobic protection

• Months of shine

• Easiest to apply

• Perfect for saltwater environments

✔ Tip: The more UV protection, the less oxidation you deal with later.

6. Clean Windows, Vinyl, & Metal

A full fiberglass detail isn’t complete without the finishing touches:

• Glass cleaner for windshields

• Vinyl cleaner + protectant for seats

• Metal polish for rails and cleats

These small areas dramatically improve the overall look.

7. Final Rinse & Dry

Rinse to remove any residue and dry with a chamois or microfiber drying towel to avoid water spots.

If the water beads strongly, your protection is working!