Antifouling: how to choose the right paint for your waters and your boating
Fouling on the hull slows a boat down, increases fuel consumption and, over time, can damage the gelcoat and the running gear. Antifouling paint is the main defence, but no single product works everywhere. The right choice depends on where the boat is kept, how warm and salty the water is, how fast the boat goes and how often it leaves the berth.
Most paints fall into two broad groups. Self-polishing (ablative) coatings wear away slowly as the boat moves through the water, constantly exposing fresh active layers; they suit sailing yachts and slower motorboats that are used regularly. Hard coatings form a tougher film that stands up to frequent cleaning and higher speeds, which is why they are common on fast motorboats. Some hard paints lose effectiveness once exposed to air, so check whether the boat can be lifted out and relaunched without recoating. If the boat rarely leaves its berth, look for a product the manufacturer recommends for low activity.
The water matters as much as the speed. Warm, salty seas such as the Mediterranean encourage heavy growth of weed and barnacles, so owners there often choose stronger formulations or add an extra coat along the waterline. Fresh and brackish water, in rivers, lakes and parts of the Baltic, has different fouling, and some products are made specifically for it.
Before buying, find out what is already on the hull. Not every paint can go over another type: switching between self-polishing and hard coatings may require a primer or barrier coat, and a thick build-up of old layers is sometimes best removed completely. Preparation decides the result: wash and degrease the hull, sand off loose paint, repair damage and follow the drying times and temperature limits in the data sheet.
Metal parts need their own products. Outdrives, saildrives and propellers are often made of aluminium or bronze, and ordinary copper-based paint can cause corrosion on aluminium. Use a coating intended for underwater metals and never paint the anodes.
Finally, rules differ between countries and even between marinas. Some areas restrict certain biocides, limit hull cleaning in the water or require wash water in the boatyard to be collected. Ask your marina or yard what is allowed before you start. If you would rather leave the job to professionals, you can find boatyards, hull-care services and marinas near you in the NautMap catalogue.