How to Paint Previously Painted Bottoms Like a Pro

How to paint previously painted bottoms

The condition of any existing coating is important to provide a sound surface for the new antifouling. If the paint is in poor condition, remove it with Interstrip 299E and follow procedure for bare work.

  • Option A- Known antifouling
    Check for compatibility; see the compatibility chart at www.yachtpaint.com. If you know what antifouling is currently on your boat, you can quickly determine whether your Interlux paint choice is compatible.
    1. Remove all traces of loose paint, dirt, grease and other contamination by wiping with Interlux Special Thinner 216. Sand with 80-grit sandpaper. Remove sanding residue.
    2. Apply 2 coats of Interlux antifouling.
  • Option B- Unknown; prime before painting
    If you do not know what the old antifouling is on your boat, it is still easy. Use Primocon as a tiecoat primer. Then simply overcoat with the Interlux bottom paint of your choice (not compatible with VC 17m, VC 17m Extra, VC Offshore or Baltoplate).
    1. Remove any loose, flaking areas with a scraper. Sand with 80-grit sandpaper. Rinse with fresh water and allow to dry before applying the new antifouling. If the old coating is in poor condition it is advisable to remove it. Apply Primocon primer directly to the old antifouling.
  • Option C- Unknown; remove
    If the old paint is in poor condition remove it. For removal, we have the easy solution, Interstrip paint remover. Its compatible with your valuable fiberglass hull and can remove several coats of paint in one application. After stripping, you are ready to prime and paint your newly cleaned hull.

Important: Now that you have stripped your hull, its important to inspect for any gelcoat damage before repainting. Also, consider applying our industry-leading InterProtect 2000E gelcoat blister protection system, to prevent long term water osmosis damage.

Applying Antifouling

  1. Ensure you are wearing the recommended protective clothing and eyewear. Information on this can be found on the label or at yachtpaint.com. Stir the paint thoroughly before application. It contains very heavy compounds, which can settle to the bottom of the can.
  2. Common application methods include roller or brush. Spray application can be undertaken, but requires specialized equipment.
    • Roller application: Use a good quality, 3/8 ths inch nap solvent resistant roller.
    • Brush application: Use a large width brush. The finish will not be as smooth as a topside paint, therefore, the type of brush used is not critical.
  3. It is very important to apply the correct thickness of antifouling even if it means putting on an extra coat. Everyone applies paint differently, so take care to apply all of the paint calculated using the guidance at the back of this manual. Normally recommended thickness is achieved by the application of two coats.
  4. Apply an extra coat to all of the leading and trailing edges, waterline, trim-tabs, outdrives, keel and rudder. High turbulence in these areas tends to wear the antifouling faster.
  5. Follow overcoating times and immersion times carefully. These are the biggest causes of antifouling detachment. Water is a very aggressive environment for paint and it is therefore very important that the paint is allowed to dry thoroughly, before launch.
  6. Usually Special Thinner 216 is suitable as a thinner and equipment cleaner. This does not apply to all antifoulings, so please read the label before application. It is best to clean equipment immediately after use.
  7. Except for the first coat on bare wood thinning antifouling paints is not advised, but up to 10% may be added to aid application in very hot or windy conditions.

The information provided here has been reproduced courtesy of Interlux. Wholesale Marine reproduced this information 08/14/2009.