Don’t Let a Through-Hull
Become a Sink Hole
Part 3: Periodic Inspection
By Capt. Ken Kreisler — April 2003
Inspection in the Water
The best preventive maintenance for seacocks, both plastic and metal, is to periodically open and close each valve. Leaving a valve in one position for an extended period of time can allow it to freeze up. Manufacturers’ guidelines may differ slightly, but the consensus is that the handle of each seacock should be moved throughout the full open/close path every few weeks, or at least once every 30 days, more frequently if possible. One school of thought advocates closing all seacocks each time the boat is left unattended. If you follow this diligent strategy, be just as methodical coming back aboard, especially to make sure valves on the raw-water intakes are open before starting the engines. Consider hanging a placard on the ignition switch(es) as a reminder.
If a seacock won’t operate freely, disassemble and lubricate it. To lubricate seacocks while a boat is in the water, use the following procedure:
close the valve
When the boat is hauled, perform steps four to six from outside the hull to lubricate the opposite side of the valve mechanism. Use winch, wheel bearing, or water pump grease. Avoid lithium or other metal-based greases, which may cause galvanic corrosion.
If a seacock is completely frozen, it’s best to haul the boat before attempting repair or replacement. If that’s not possible, then temporarily plug or seal the penetration from outside the hull before attempting repair. Don’t be like the guy who sank his boat at the dock while battling a stubborn seacock. The handle wouldn’t turn, so he put a 20-inch Stilson wrench on the valve stem for leverage and proceeded to rip the entire valve off of the through-hull fitting.
Out of sight and easily overlooked, neglected seacocks and through-hulls can cause untold grief. But with regular checks and minimal care, they’ll provide years of reliable service.
This article originally appeared in the March 2003 issue of Power & Motoryacht magazine.