Thru-Hull Fittings Maintenance

The inspection and maintenance of thru-hull fittings is simple enough, although it does require hunting around in the bilge to find the below waterline thru-hulls

Boat thru-hull fittings

This boat maintenance job is easy to overlook, but the failure of a thru-hull fitting or seacock can result in the sinking of a boat. Inspection and maintenance of thru-hull fittings should be done at least once a year. Here are some tips on doing thru-hull fitting maintenance.

Maintenance Within the Hull

All seacocks attached to thru-hull fittings should be cycled open and closed a few times every month to keep them lubricated and prevent them from getting stuck. 

Maintaining Older Bronze Seacocks

  • Dismantle them 
  • De-grease with a solvent
  • Lightly refine the surface with wet or dry sandpaper
  • Re-grease with water-resistant grease and reassemble

Older bronze seacocks that use a tapered cone system should be fully dismantled, any old grease removed with a solvent, the surface lightly refined with wet or dry sandpaper, then re-greased with water-resistant grease and reassembled. 

Evercoat marine acetone solvent

Sierra marine grease

PRO TIP: You can use a zerk fitting to add new grease, but because the fitting will corrode, it shouldn’t be left in the seacock. 

Maintaining Newer Bronze Seacocks

  • Grease the ball by removing the attached pipe or hose, de-grease, and then re-grease
  • Cycle the seacock’s handle to spread grease around the ball valve

Newer seacocks use ball valve systems. Grease the ball by taking off the pipe or hose that attaches to the seacock, then removing any water and old grease, applying new waterproof grease to the ball with a paintbrush and re-attaching the pipe or hose. Next, cycle the seacock’s handle a few times to distribute the new grease around the ball valve. 

Perko bronze thru hull fitiing

Perko bronze thru hull adapter

Inspect the backing blocks on which the seacocks are mounted to ensure they’re intact. If any backing blocks are losing their integrity, the boat has to be pulled from the water, the hull fitting removed and the block replaced. Trace all the bonding wires to ensure that each through-hull fitting is properly connected to the boat’s bonding system.

Maintenance Outside the Hull

Inspect all thru-hull fittings whenever the boat is out of the water. Remove any marine growth on the outside of the fittings and from the inlet part of the thru hull. Ensure the fitting’s inlet is free of debris or blockages, and that water can pass through it with ease.

Thru hull fitting maintenance

Replace Fittings as Soon as Possible

Any thru-hull fittings that are damaged or can’t be unblocked must be replaced immediately, as should any seacocks that are jammed or can’t fully open or close. Remember, if a thru-hull fitting fails and the seacock is unable to close, the boat will flood and possibly sink. 




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