Whether you have a super high performance racing yacht or a modest fishing boat, chances are you are going to have to apply an antifouling coating to the bottom of the boat at some stage.

This is especially true for those boats that are moored or spend considerable time in the water. In these situations it is likely that the boat will need antifouling every 1 to 2 years.

The main purpose of bottom paint is to slow the growth of barnacles, algae, and other marine organisms on the underside of the boat that can reduce the vessel’s performance.

In years gone by, sheets of thin copper were applied to the hull of the boat to reduce the build-up of marine growth. Although this method would now be considered inefficient by today’s standards, copper-based coatings are still used in many modern bottom paint products.

Due to increased scrutiny about the environmental effects of copper-based bottom paints, many paint manufacturers are also bringing out eco-friendly variations that contain little or no copper.

Applying bottom paint yourself is not as difficult as you may have imagined. Here is an overview of the steps involved.

  1. Choose the correct anti-foulant to match the material being coated. It is important to check the compatibility of the old paint with the new bottom paint (paint manufacturers will have compatibility charts to guide you). For aluminum hulls or underwater metal, you’ll need a specialised paint to avoid corrosion.
  2. Prepare the surface well before painting. This will help the paint adhere well and provide a longer-lasting coating. If the existing bottom paint is in very bad condition, you may need to remove it using a power sander or paint stripper. In many cases however, this is not required. Simply clean the hull with either a power-wash or an acid-based bottom cleaner, give the area a good sanding with 80 grit paper, rinse with water and then apply a suitable primer (according to manufacturers instructions).
  3. Mask off any borders with painter’s masking tape.
  4. Apply the bottom paint according to manufacturer’s instructions. It is recommended avoiding using a sprayer to apply the paint. For ‘Do it yourselfers’, a roller works very well and is surprisingly efficient. Be sure to use the correct roller to suit the type of bottom paint being used.

Tips:

  • Wait until the weather is ideal for painting before starting the job. Most manufacturers recommend painting when the temperature is between 60°F / 16°C and 80°F / 27°C with humidity less than 65%.
  • Choose the right paint based on the type of boating you will be doing and the compatibility with existing paint or material being coated.
  • Always consult your local boat chandler or marine dealer for advice when selecting bottom paint.
  • Be patient and try not to rush the job. Allow plenty of time to complete the process.
  • Make the most of the time that the boat is out of the water. Repair any damage to the hull, rudder or keel. Inspect the propeller and outdrives. Check anodes and perform any other maintenance.