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Don't neglect your seacocks

These humble handles keep the water out

More than 40 percent of boats that sink do so at the dock or on a mooring, and the majority of these can be attributed to water flooding into the boat through an underwater skin fitting, according to insurer BoatUS.

Even a modest vessel will likely have a number of through-hull fittings below the waterline — engine water intakes, saltwater washdown pump, live well, head intakes, waste outlets, and so on. Every underwater through-hull to which a hose is fitted should be protected by a seacock. These unseen components are critical but are rarely given a second thought by many boat owners.

A seacock is a valve that allows the flow of water to be shut off. They can be manufactured from a number of materials, but the most popular are bronze and Marelon (a reinforced plastic). All seacocks have a handle that moves 90 degrees from fully open to fully closed, and many have a lever-type handle. When the handle is in line with the outlet, the seacock is open; when it’s perpendicular to the outlet, the seacock is closed. This means you can tell at a glance if the seacock is open or closed.

As surveyor, I come across gate valves more often than I should. These are often installed by the boat owner to save money. Gate valves are unsuitable for number of reasons. A round knob handle renders it impossible to tell at a glance if the fitting is open or closed. Also, these gate valavess are made for domestic use, and the materials they’re manufactured from — often cheap brass — aren’t intended for the marine environment. Brass is an alloy of copper and zinc, two metals that are far part on the galvanic scale. When immersed in an electrolyte, such as seawater, the fitting degrades in a process called dezincification. The zinc is consumed, which leaves behind the soft copper and leads to the failure of the fitting. Bronze, on the other hand, is made up of copper and tin — far more noble metals that won’t suffer this fate.

A seacock’s most important role is shutting off the in-rush of water should a hose let go, so it’s crucial you can reach and operate the seacock. You should know the location of every seacock on your boat. Boatbuilders sometimes put then in awkward places, which is why they often go ignored and are left open from season to season. One of the best ways to maintain a seacock is to regularly exercise it. A seacock that is frequently closed and opened will freely operate.

If you haul your boat for winter, grease your seacocks if the manufacturer recommends it, but be sure to use only the recommended lubricant. Never use lube that contains graphite, which is at the top end of the galvanic scale and will consume the lesser metals in the seacock. I close all of the seacocks on my boat if I am leaving it for more than a few hours. This not only exercises the fitting but forces me to check hose connections and clamps, which are a major contributor to keeping the water on the outside of the boat.

Even if your seacocks are in perfect working order, it won’t make a difference if the hose that connects to it is in poor shape. Hoses showing signs of fatigue or deterioration should be replaced without delay. The American Boat & Yacht Council recommends that all hoses be double clamped if they’re connected to a skin fitting or seacock that’s below the boat’s normal static waterline. Clamps should be oriented with the tightening screws at 180 degrees to each other and constructed of quality stainless. Home-store clamps are usually made of inferior metals, and even if the band is stainless, the screw often is not. Here’s a tip: Quality stainless is not magnetic, so check your clamps’ construction with a small magnet.

A seacock failure can sink your boat, so it pays to be prepared. Of course, the first order of business is to close the seacock. Also, keep a tapered softwood plug near each seacock. If the seacock breaks off, these can be hammered into the hole to slow the flow of water. Rags also can slow the in-rush of water. You may be unable to stop all of the water coming in, but the bilge pumps will have a better chance of staying on top of it.

See related articles:

- Eyes in the back of your head

- Practice, practice, practice

- Think ahead

- Keeping a lookout

November 2014 issue