How To Bottom Paint a Boat Properly (Anti-fouling Paint)

Whether you do it yourself (DIY) or hire a company like Bluewater, it’s important to regularly bottom paint your boat to prevent sea life build up and protect your hull.

You can ensure the job is done properly by your boat service company or yourself by following these tips.  This assumes the boat has previously been bottom painted and is in need of an annual recoating.

  1. Set-up:  Have the boatyard pressure wash your boat to remove sea life, saltwater and residues.  Once the boat is blocked, start by taping the waterline all the way around the boat using a painter’s tape that is easily removed and has some resilience to UV.  The tape should be positioned on the white gelcoat or coloured bootstripe with the bottom edge perfectly flush with the legacy bottom paint (assuming the waterline does not need to be moved).  In most boatyards around Vancouver and BC the boat needs to be rigged with tarps from the railing to the ground to capture dust and protect other nearby boats in the yard.  If there is rain in the forecast, it’s wise to install a rain catcher about 30 cm above the tapeline using any kind of plastic channeling.   This will prevent water streaks.
  2. Sanding:  Use a dustless sander or other sanding equipment to lightly sand the entire surface (80 grit is a good choice) preparing a clean solid surface for the new application.  Don’t oversand, as long as there are no paint flakes or other contamination, you’ve done enough.  Be sure sanding dust does not drift to other boats and clean up all dust from the ground with a vacuum, broom or use of drop sheets in advance.  Check with your local boatyard for rules.
  3. Painting:  Be sure the paint you select is compatible with previous coats by reading the manufacturer’s instructions.   Micron CSC is compatible with many paints and is a high quality ablative paint that polishes off gradually in the water to release the boicide that minimizes sea life build up.  Bluewater uses Micron CSC for about 90% of client boats.  Most antifouling paints can be applied at a broad range of temperatures but curing times vary.   Be sure to thoroughly stir the paint so it is homogenous.  Use a paint tray, roller and broom handle extension if helpful to roll a nice even coat on all previously painted surfaces below the waterline.   Do not apply to propellers, shafts, sonar transducers or other equipment that isn’t already painted.  For proper application, it’s important to let the anti-fouling paint fully cure, usually 16 hours but may be as high as 36 hours in cold temperatures – check the instructions.  Our marine technicians often use the finger nail test – if pressing your finger nail into the paint does not leave a mark and the prescribed time has passed, it’s ready for the next coat.   Any subsequent coats can be applied directly with no additional sanding.  Manufacturers recommend 2-3 coats.  Most of our clients find 2 coats is good for an annual cycle.
  4. Launch:   It’s important to allow the last coat sufficient time to properly cure (usually 16 hours but varies with temperature) before the boat is lifted back into the water.   Be sure to remove the painters tape, tarping and clean up prior to launch.   We also recommend getting a few pictures of the hull out of the water for comparison at the next haul out or to provide to a boat repair shop, boatyard operator, dive company or insurance company.
  5. Other service items:  While the boat is out of the water and in close proximity to marine service shops, consider changing your anodes (zincs), servicing sterndrives or legs, inspecting running gear (prop, shaft, cutlass bearing), cut and polish the boat hull, annual engine service or any maintenance on thru-hulls.  Common upgrades during a haul out include sonar transducers for depth/fish finder/sonar, underwater lights or bow thruster installation/ maintenance.

Contact Bluewater to take care of your next bottom paint and enjoy the water!

Boat Bottom Paint
Boat Bottom Paint
Boat Bottom Paint Service Vancouver