Boat Hull Cleaner - Stain and Rust Remover for Marine Surfaces

MA5X Hull Cleaner is a concentrated phosphoric acid formula that removes waterline stains, rust, algae, barnacle residue, scum, and yellowing from fiberglass, gel coat, lower units, and trailers. It targets alkaline marine buildup where soap can't reach and delivers strong cleaning performance without the harsh fume profile of hydrochloric acid hull cleaners. Because it's concentrated, one bottle goes significantly further than ready-to-use alternatives.

How to Use

For heavy rust, waterline stains, and marine growth, apply concentrate directly with an acid-resistant sprayer or brush on cool, dry surfaces. Allow up to 10 minutes of dwell time, then rinse thoroughly with fresh water. For routine maintenance and lighter staining, dilute 1 part concentrate to 4-5 parts water. Always test on a small area first, and avoid prolonged contact with metals and sensitive coatings.

What It Works On

Formulated for fiberglass, gel coat, painted hulls, lower units, and marine trailers when used as directed. Effective in both fresh and saltwater environments. Rinses clean with minimal streaking.

Safe Handling - Required Before Use

Signal word: DANGER. This product causes serious eye damage and skin irritation on contact. Wear rubber gloves and eye protection whenever handling. Avoid breathing mist or spray. Keep out of reach of children. If eye contact occurs, rinse with water for at least 15 minutes and seek medical attention immediately. Do not mix with alkaline products or store near oxidizers.

This is a phosphoric acid solution (pH 1–3). It is non-flammable and biodegradable. View the full Safety Data Sheet (SDS).

Made in the USA. Available in 32 oz and 1 gallon.

Marine detailers, boatyards, and fleet service operations can order Hull Cleaner in a 55-gallon drum through our Bulk & Wholesale collection.