How do I choose the right antifouling paint for my boat and waters?
My 10-metre fibreglass cruising yacht stays afloat in a sheltered saltwater marina from April to October and usually sails at weekends. I don't know what antifouling is already on it. Should I choose self-polishing or hard paint, and how much does the local water matter?
Answer
Choose antifouling to suit your hull material, local fouling, cruising speed and time afloat; self-polishing paint is the usual starting point for a cruising yacht, while hard paint suits fast motorboats and frequent handling. Before buying, identify the existing coating and ask nearby owners what lasts a full season, because compatibility and local conditions matter more than the brand.
Check hull and existing paint
Check old invoices or ask the previous owner for the exact product name. Colour alone cannot identify a coating. Painting over an incompatible or flaking layer wastes the job.
- Fibreglass: conventional antifouling usually goes over a sound, compatible coating or the specified primer. An epoxy barrier coat protects the laminate and forms a separate part of the system.
- Aluminium: use a product explicitly approved for aluminium, with its specified primer system. Conventional cuprous-oxide antifouling can cause serious corrosion.
- Steel or wood: choose a system approved for the substrate and maintain the required protective primer beneath it.
- Saildrives, outdrives and propellers: treat these separately with coatings approved for their metals; ordinary hull antifouling is often unsuitable.
If the old coating is sound and identified, follow the new paint manufacturer's compatibility chart. An unknown coating may need a specified tie-coat, but loose paint must come off first. Silicone foul-release coatings generally need specialist preparation before another system will adhere.
Match paint to boat use
Self-polishing antifouling gradually wears away, exposing fresh active material. It is the normal choice for displacement motorboats and cruising yachts used regularly through the season. Renewal is typically annual. Check the product's speed limits and suitability for drying moorings or periods ashore.
A sound self-polishing coating may need only thorough washing before recoating, according to its instructions. Residual layers still accumulate. Complete removal may be needed after roughly 5 to 15 years, or sooner if adhesion fails.
Hard antifouling leaves its binder behind as active ingredients are released. Its resistance to rubbing suits fast motorboats, trailer contact and racing hulls that need a smooth, burnished finish. The exhausted coating builds up, so expect controlled sanding annually or every second year.
Traditional soft antifouling erodes more readily and is associated particularly with wooden boats and cutters. It is not interchangeable with modern self-polishing paint: changing between soft, hard and polishing systems may require removal and priming.
International, Hempel and Jotun offer established marine coating ranges, but compare each product's technical data sheet before choosing by brand.