How to Repair the Cavitation Plate on an Outboard Motor

The lower unit section of an outboard motor is extremely vulnerable to underwater objects that the driver of the boat cannot always see, such as sunken rocks, logs, or even sunken boats. The cavitation plate, also known as a skeg, is a fin-shaped trim piece located at the bottom of an outboard motor's lower unit. It is commonly made of metal but can be made of fiberglass too. If the skeg gets dented or punctured it can be repaired, which will save the expense of having to buy a brand new lower unit.

Things You'll Need

  • Pliers
  • Old newspaper
  • Hack saw
  • File
  • Orbital sander
  • 36-grit sand paper
  • Rag
  • Masking tape
  • Epoxy
  • Spray paint primer
  • OEM factory marine spray paint
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Instructions

    • 1

      Dry dock the boat on a trailer and tilt the outboard forward so that the propeller and cavitation plate are a little lower than chest level. Use pliers to remove the cotter pin holding the propeller nut in place and then remove the propeller nut. Stuff the propeller hole area with old newspaper.

    • 2

      Use a hack saw to cut away the damaged section or a file to smooth out small holes.

    • 3

      Clean the area thoroughly with a rag. Wipe off any dirt, grease or grime. Once the area is clean sand it down with 36-grit sandpaper and rotary sander.

    • 4

      Tape the bottom side of the hole with masking tape.

    • 5

      Mix the epoxy according to the instructions on the packaging and fill the hole or crack in. Allow at least 12 to 14 hours for the epoxy to set.

    • 6

      Sand the repaired area again once the epoxy has dried.

    • 7

      Cover the area with a layer of spray paint primer and allow it to dry. Once the area is dry spray paint the cavitation plate with OEM factory marine spray paint.