A clean hull is free speed and free fuel. A fouled one can cost you several knots, raise fuel consumption noticeably and make the engine work harder and hotter. In the warm water of the south-east Spanish coast, and especially in the Mar Menor, marine growth doesn’t take long to get established, so antifouling is a yearly job for most boats that live afloat.
Why the Mediterranean is hard on hulls
Sea temperatures here can reach the high twenties in August, and the shallow Mar Menor is warmer still. Warm, sunny, nutrient-rich water is exactly what weed, slime and barnacles love. Boats that sit on a mooring for weeks without moving are the worst affected, because self-polishing paints rely on water flow to work.
Types of antifouling
Self-polishing (ablative) antifouling wears away slowly as the boat moves, constantly exposing fresh biocide. It suits most leisure motorboats that are used regularly and lifted once a year. It doesn’t build up thick layers over the years, which keeps future preparation simple.
Hard antifouling forms a tough film that doesn’t wear away. It suits faster boats and those that are regularly scrubbed or kept on trailers or dry stack and launched often. The downside is that layers build up and eventually need removing.
Hybrid and specialist coatings combine features of both. There are also copper-free formulations, and specific products for aluminium drives and outboard legs, where ordinary copper-based paint can cause corrosion.
Never put copper-based antifouling on aluminium outdrives or outboard legs. Use a product designed for aluminium.
When to antifoul
The ideal window on this coast is late winter to spring, from February to May, so that the boat goes into the season with fresh paint. Many owners combine it with the annual service and an anode change while the boat is out of the water.
As a rule of thumb, most boats kept afloat all year will need antifouling every twelve months. Boats on dry stack, lifts or trailers may go longer, or may not need it at all if they are washed after every use.
What a proper antifouling job includes
- Lift and pressure wash as soon as the boat comes out, before the growth dries hard.
- Inspect the hull for blisters, impact damage and gelcoat cracks.
- Prepare the surface: light sanding to key the old paint, and removing any loose or flaking layers.
- Mask the waterline for a crisp finish.
- Apply the antifouling, usually two coats, with extra coats on the leading edges, the waterline, the rudder and the keel where wear is highest.
- Replace the anodes on the hull, trim tabs, shaft and drives.
- Service the propeller and drive while access is easy.
- Relaunch within the time window the paint manufacturer gives.
Making it last
- Use the boat. Self-polishing paint works best when the hull moves through the water.
- Avoid scrubbing hard on self-polishing paints; a soft brush or cloth is enough.
- Book a mid-season hull clean if your boat sits for long periods.
- Keep the waterline clean so weed doesn’t creep up on to the topsides.
Environmental rules
Antifouling paints contain biocides and are regulated in Spain and the EU. Hull scraping and pressure washing should be done in boatyards with proper wash-water collection, not on public slipways or beaches. Using a professional yard protects the water we all enjoy, especially the fragile Mar Menor.
Our antifouling service
We lift, wash, prepare, antifoul and relaunch craft of all sizes, and replace anodes and service the drive at the same time. See our antifouling and hull page, or book a service to reserve a spring slot before the rush.
