How to Remove a Seacock Through a Hull Fitting

Updated April 17, 2017

Seacocks, or through-hull valves, control the water's flow into or out of a boat. Boat manufacturers install seacocks and through-hulls on the engine's cooling water intake and marine toilet output lines, among other locations. Seacocks also enable an owner to shut off seawater flow into the boat if a hose or fitting fails. A boat owner places a seacock in the "closed" position when he leaves the boat unattended. Owners should always maintain the boat's seacocks so each device can serve its intended purpose. An owner should immediately remove and replace a non-functioning seacock.

Remove the hose clamps from the hose attached to the seacock. Use a flat blade screwdriver.

Remove the hose from the seacock's hose barb. Twist the hose while pulling it. Cut the hose off with a utility knife if the hose is too stiff to slide off the hose barb.

Obtain a through-hull step wrench. You may be able to borrow one from your boat yard. If not, purchase one from your marine supply store.

Heat the through-hull fitting with a heat gun. This softens the sealing compound.

Insert the step wrench into the through-hull from outside the boat. Through-hulls have two lugs that extend into the through-hull fitting's interior. Align the step wrench slots with the lugs.

Place a long adjustable wrench on the step wrench flats. Remove the through-hull from the seacock. Turn the wrench counter-clockwise. Unscrew the through-hull from the seacock.

Remove the bolts that attach the seacock's body to the hull. Use a box wrench on the inside nuts. Use an assistant with a flat blade screwdriver on the outside.

Remove the bolts. Drive the bolts out with a punch and hammer.

Remove the seacock. Drive a putty knife between the seacock's base and the hull. Cut the sealant bond by swinging the putty knife from side to side.

Lift the seacock off the hull.

Remove all old sealant from the hull's exterior and interior. Use a razor blade.

Things You'll Need

  • Flat blade screwdriver
  • Utility knife
  • Heat gun
  • Though-hull step wrench
  • Long adjustable wrench
  • Box wrench set
  • Punch set
  • Hammer
  • Putty knife
  • Razor blade
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About the Author

Robert Osborne has written professionally since 2010. He writes for eHow, specializing in aircraft and boat maintenance, home renovation and electrical engineering. Osborne earned his Bachelor of Science in electrical engineering from George Washington University.