It's very important to grease the keel screw every 2nd year.
  It looks difficult but it's really easy. The screw is a naval bronze jackscrew
  and very strong, but the shape of the keel lends itself to damage if sailed
  into a rocky shoal at high speed. As a precaution after launching, always
  lower the keel in shallow water at the dock in case it decides to fall off the
  boat and go to the bottom.
  
  On dry land, (as on a trailer) block up the centreboard in the fully retracted
  position from under the hull. Remove all the stainless screws holding the
  fiberglass cover onto the centreboard trunk top. Inside there are 4 large pop
  rivets holding the metal screw plate retainer down. Drill these out. Using the
  square wrench provided for the purpose, turn the square nut counterclockwise,
  raising it and the screw out of the lead keel assembly. Raise it as far as
  possible and grease the jackscrew with waterproof yacht winch grease (get this
  in the sailboat chandlery). Grease the nut at the bottom, and screw it all
  home again. Take this opportunity to check and if needed replace the ball
  bearing race. The bearing race is readily available from C&L Boatshop.
  
  If the screw seems to bind too much when first raising it, either the grease
  is really dry, (Squirt oil down the shaft) or the screw has been bent from
  running the boat aground. (hopefully NOT!)