Antifouling your boat is one of those tasks that you dread. Antifouling can be overwhelming. Not only is the selection of paints confusing, but also the preparation and application are crucial if you’re looking for the best result. Antifouling is a vital but challenging job that must be done under the water. It should therefore always be applied with the best conditions.

Step-by Step Guide For Prepare Your Boat To Antifouling

1. Wear protective clothing when dealing with antifouling. This includes full overalls, a face mask, goggles, gloves and a face mask.
2. Consider wearing a hat if your overalls do not have a hood to protect your scalp from toxic paint.
3. When the boat comes out of water, jet/pressure wash it to remove all growth, dirt and flaking/old antifoul.
4. Remove any loose antifoul using a paint scraper if you find small flaking areas.
5. Consider stripping your boat down to the gelcoat if the antifouling has become particularly loose. If you want to accelerate the process, it may be worth hiring a professional.
6. Mark the waterline as soon as possible!
7. Keels require special attention. Cast-iron surfaces should be polished before antifouling. Lead keels must have the oxide layer removed and all grease or contamination removed.
8. Before using, thoroughly mix all paints.
9. Before priming, make sure you have the correct primer for your anti-fouling paint.
10. Be aware of anodes which should not be painted or surfaces requiring a different antifouling.
11. Masking tape can be applied to the edge of the waterline for a clean, crisp look.
12. Use rollers to apply primer and antifouling. Antifouling paint can be sprayed, but only by professionals.
13. Check and follow the minimum immersion and overcoating times. These will be listed on the tin.
14. Most boats can get away with one coat of primer followed by two coats antifouling. It is also recommended to apply a third coat on high-wear areas such as the waterline and keels.

Out With The Old

It’s crucial to pressure-wash the hull as soon as your boat is ashore to remove any previous antifouling. It’s much more difficult to remove the old paint if it’s dried.

You can remove loose or flaking Antifoul with a paint scraper if you discover it while pressure-washing. If you see a lot flaking and many layers of antifouling, you might want to strip back the hull to remove all the antifouling.

Antifouling dust can be extremely dangerous, so removing it should only be done with extreme caution and plenty of personal protective equipment (PPE). You can do this yourself by wet-sanding or using a chemical paint stripper that is formulated to be used on fibre glass.

When removing antifouling, it is important to wear protective clothing including goggles, and a facemask. Although a cheap mask may be tempting, it is not strong enough to protect you from the toxic dust created by removing antifouling.

It’s best to hire someone to prepare your hull if you aren’t confident. The cost of hiring a contractor who has experience in antifouling removal can be offset by the time saved.

Even after the antifouling is removed, it’s easy to see the waterline. It’s still a good idea, however, to mark the waterline prior to moving forward with the antifouling procedure to ensure that you can correctly reinstate it.

You may want to measure at 2 foot intervals the distance between the waterline and the gunwale before removing the previous layers. This is just in case the waterline can’t be easily seen once the boat has stripped down.

Prepare The Hull

It’s essential to take the time to prepare and prime your antifouling properly if you want it to look good, last long, and do its job. The smoother/flatter the surface is, the better.

It is especially important to do this if your boat is fast or racing, because a rough surface can increase drag and cause you to slow down. A rough surface will also make it difficult for the antifouling to adhere to a boat.

After you have removed the old antifouling layers, you will need to paint the hull with an antifoul primer. You have a wide range of primers to choose from, so be sure to select one that matches the type of antifouling you will be using.

You may want to apply an epoxy coating if you have stripped your boat down to the gelcoat. This will protect against osmosis. Talk to an Boat surveyor First, test the moisture level in the hull. Sealing in excess water will only lead to further problems.

You might worry about applying new antifoul if you have left any or all of the antifouling from last year on the hull. Modern antifouling is much easier to apply over old coats. If you are unsure about the antifouling, you can use a primer to ‘tie-coat’ between them. You can benefit from a fresh start without having to strip the boat back.

Care For Keels

Antifouling also needs to be applied to your boat’s keel. Make sure that they are perfectly faired so the antifoul can adhere to the surface.

1. Before painting, remove any rust from your cast-iron keels with an angle grinder. The metal surface should be smooth and bright.
2. You can remove the oxide layer from unpainted lead keels by using a wirebrush or emery-paper in an electric drill. Then, wash the area thoroughly with a suitable cleanser before priming it with an etch primer.

After you have prepped the keels you can apply the primer recommended for your chosen antifoul.

Gathering Your Equipment

You might think that the colour of your antifouling paint is enough to stir it. But you would be wrong. Antifouling paints often contain more than 50% solids, which settle to the bottom during storage. It’s important to shake and stir your antifoul before you apply it. This can be done with a stirring device that is designed to work with a cordless tool.

Use a small to medium pile roller with an extendable handle for the fastest and cleanest way to apply antifouling. It keeps you at a safe distance from the paint, reducing the need to bend and stoop. While it may be tempting to use larger rollers to speed up the process, they absorb more paint and, given the high cost of antifouling, the extra paint will usually outweigh any time you save.

Spraying antifouling paint on the hull can also speed up the process. Due to its toxicity, antifouling should only be applied by trained professionals who have the appropriate equipment.

It is important not to paint over the anodes on the shaft or hull sacrificials. This will prevent them from working properly.

Check the manual before antifouling your aluminium outdrives. They may require a special antifoul for the hull.

To protect yourself from paint contact, you should wear a mask, goggles, overalls and gloves when applying antifouling. Wear a hat if your overalls do not have a hood. It is easy to rub the bottom of the hull with your head, which can be embarrassing and toxic.

Get Painting

You will require:

• Paint roller and tray
• Replacement rollers
• Sanding paper that can be used both wet and dry
• Different sized paint brushes
• Masking tape
• PPE

It’s now time to paint. Gather your tools and apply masking tape along the waterline.

Apply the antifouling in thin, even layers, and avoid drips or runs. Paint thinners and a thorough stirring of the paint will ensure that it has a uniform texture.

Start at the waterline, then work down. Keep some paintbrushes on hand to cover those difficult-to-reach places, such as around the rudder and propellers.

Check the drying time carefully, and make sure the antifouling is dry completely before you apply the next coat. It’s important to let the antifouling paint dry completely before you launch the boat, even though some will go off under water.

How Many Coats Are Required?

If the boat will be ashore for only a few days or the local fouling conditions is very weak, it’s recommended to apply at least two coats every sailing season. Apply a third coating around the rudder, keel and waterline of sailing boats.

You shouldn’t stretch out the antifouling. To ensure that the antifouling is effective, it’s important to apply as much biocide as possible to the hull. It is better to buy another tin of biocide to ensure an effective antifouling and a thorough coating than to risk damaging the hull.

Failure to follow the minimum immersion and overcoating times, which are usually clearly specified on the tin, is the main cause of flaking.