How to Wet Sand Gelcoat on Boats for a Mirror Finish (600–2000 Grit Workflow)

Boat gelcoat takes the brunt of sun, salt, and water damage—eventually fading or oxidizing. Wet sanding restores that glossy showroom finish by removing the dull top layer and preparing the surface for polishing. This guide covers how to wet sand and polish gelcoat safely without cutting through to fiberglass.

Why Wet Sanding Works for Gelcoat

Gelcoat oxidation appears as chalky white film that dulls color. Wet sanding removes the oxidized layer evenly and smooths scratches before polishing. By working through fine grit steps, you reveal a deep, consistent gloss while preserving the protective coating.

Recommended Tools

• Wet/dry silicon carbide sandpaper (600–2000 grit range).
• Soft foam sanding pad or orbital sander with water feed.
• Bucket or spray bottle with clean water.
• Marine polishing compound and microfiber cloths.
• Rotary polisher (optional for faster buffing).

Ideal Grit Sequence

• 600 grit – Remove oxidation and faded surface layer.
• 1000 grit – Refine scratches and even color tone.
• 1500 grit – Prepare for high-gloss polishing.
• 2000 grit – Final micro-sanding before buffing.

Step-by-Step: Wet Sanding Boat Gelcoat

1. Clean the hull. Wash with marine soap to remove salt, grease, and residue. Dry thoroughly and inspect for cracks or deep scratches.
2. Start removing oxidation. Use 600 Grit (25-pack) wet/dry paper to sand faded areas. Keep the surface continuously wet to prevent clogging and control heat.
3. Refine with mid-grit. Switch to 1000 Grit (50-pack) to remove any dullness left from the first pass. Sand evenly until the surface looks uniformly matte.
4. Fine-sand for polish. Continue with 1500 Grit (100-pack) paper, working in small circles. The finish should start to appear satin-smooth.
5. Final smoothing. Finish with 2000 grit wet sanding for a silky touch. Rinse the area frequently and wipe clean between steps.
6. Polish and seal. Apply marine-grade compound with a rotary or dual-action polisher. Buff until the gelcoat gleams. Protect with wax or UV sealant for lasting shine.

Special Cases

For colored gelcoats (especially dark blue or red), avoid coarse sanding unless oxidation is severe. Start at 800 or 1000 grit to preserve pigment depth. For spot repairs, sand and polish small sections only—large panels can be done in overlapping zones for consistency.

Pro Tips

• Always sand wet—dry sanding can overheat and damage the gelcoat.
• Use light, even pressure; pressing too hard can reveal fiberglass beneath.
• Rinse sandpaper often to keep grit clean and sharp.
• Inspect the surface under angled sunlight for haze before moving to the next grit.
• Apply two coats of marine wax after polishing for UV protection.

Aftercare

• Wash the hull regularly with non-abrasive soap to maintain gloss.
• Reapply wax every 3–6 months for maximum UV defense.
• Keep the boat covered when docked to prevent oxidation recurrence.
• Spot polish lightly with 2000 grit if dull spots reappear.

FAQs

• Can I use an electric sander? Yes, with low speed and constant lubrication—hand sanding is safer for thin gelcoat areas.
• How do I know when to stop sanding? When the surface feels uniformly smooth and shows no chalky areas under water.
• Will sanding remove scratches? Shallow ones yes; deeper gouges may need filler before refinishing.

Watch & Learn

Wet sanding your boat’s gelcoat with a careful 600–2000 grit progression restores rich color, depth, and reflection—leaving your vessel looking glossy and well-protected for seasons to come.