How to Build a Damage-Control Kit: Plugs, Patches and a Plan for Leaks

Walk the boat with a flashlight and list every opening: engine raw-water intake, generator and A/C intakes, head intake and discharge, sink and cockpit drains, livewell and washdown, transducers and speed sensors, the shaft log and rudder post, sterndrive bellows, and the drain plug. Note the size of each fitting and whether it has a seacock. Keep the list (a phone photo works) in the kit.

Don't skip the fittings just above the waterline. BoatUS points out that the plastic "mushroom" through-hulls used for scuppers, bilge pump outlets and livewell drains are notorious for cracking after years of sun, and a loaded boat or a wake can put them under water.

Buy tapered softwood plugs (pine or fir). Soft wood squeezes into an out-of-round hole and swells as it soaks, and it can be split or whittled to fit odd shapes. Match a plug to each fitting from your list, then tie it to the hose or seacock with a short lanyard so it is right there in the dark. Keep a few extra plugs and wedges in the kit for holes you didn't plan for.

Foam plugs are another option. BoatUS has reviewed cone-shaped plugs made of closed-cell foam that you squeeze and push in by hand, like a foam earplug, with no hammer needed. Because the foam springs back, it can conform to an irregular opening, such as a fitting that has cracked or a seacock that has broken off. Many owners carry both: wood plugs tied at the through-hulls and a foam plug or two in the kit. Practical Sailor tested one foam plug that could also be pushed lengthwise into a split, or cut with scissors to fit a broken hose or pipe, on irregular holes up to about 4 inches across. Their testers still keep a full set of wood plugs, because wood plugs come drilled for a lanyard and can hang ready at each seacock, while a foam plug is most useful kept whole in the kit for the leak you didn't plan for.

Self-fusing silicone "rescue tape" sticks only to itself, so it works on a wet, split hose when stretched tight and overlapped. It's a get-home fix, not a repair. Add a handful of all-stainless hose clamps in the sizes your boat uses, so a loose or broken clamp can be replaced or doubled on the spot.

Hull damage from a collision is usually a jagged split, not a neat round hole, so plan to improvise. The BoatUS article suggests:

• Rubber sheet or cut-up inner tube in several sizes
• Squares of thin plywood with slightly larger foam or felt gaskets, plus rust-resistant self-drilling screws and a driver to fasten them to the hull from inside
• Rags, towels or cushions you can stuff into a hole and brace with a floorboard or boathook
• A can of expanding foam to fill gaps around a wood patch
• A wax toilet bowl ring, which can seal around a shaft or gland
• Duct tape and a tube of marine sealant that cures and bonds underwater

Wrapping rubber or a caulk-soaked rag around a plug or wedge before you tap it in helps it seal and stay put.

Underwater epoxy putty is worth carrying, but don't count on it to stop active flooding. BoatUS points out that most epoxies won't stick to a wet surface with water pushing through it, can't bond parts that are moving, and cure very slowly in cold water. Use putty once a plug or patch has slowed the flow to a seep, to seal the edges.

A heavy tarp, plastic sheet or purpose-made collision mat pulled over the outside of a hole with lines lets water pressure press it against the hull. It won't seal perfectly, but it can cut a gush to a trickle that your pumps can manage. Pre-tie lines to the corners so it's ready to deploy.

Many fiberglass boats have one-piece liners that hide the hull. If the damage is behind a liner, water may be pouring out of wire and hose holes with no way to see the real breach. BoatUS suggests carrying a hatchet or small ax, a saw and a pry bar so you can cut away furniture or a liner panel to reach the hull. Add a waterproof flashlight, screwdrivers and nut drivers that fit your clamps, pliers, a knife, and a charged cordless driver.

Keep a manual bilge pump or a big bucket near the kit. On a bigger boat, a portable lever-action pump mounted on a carrying board with its own length of hose (Edson, among others, sells these as kits) can be taken to whichever compartment is flooding and run without electricity. Check that your electric bilge pumps, float switches and high-water alarm all work (see the bilge pump guide). A pump buys time; the kit is what lets you get ahead of the water.

Put everything in one waterproof bag or bin clearly labeled "DAMAGE CONTROL." Stow it somewhere you can reach without lifting the engine hatch or crawling into a locker that might already be flooded: near the companionway or helm is ideal. Don't bury it under fenders and dock lines. Larger boats may want a second small kit near the engine room.

At the start of each season (and with new guests on longer trips), show people where the kit is, where each seacock is and how to close it, where the manual pump is, and how to make a MAYDAY call on VHF 16. A crew that knows the boat can start fixing while you handle the radio. Practical Sailor suggests deciding ahead of time who drives the boat, who handles the radio and navigation, and who works the leak, so nobody stands around waiting for orders; on a small boat with two aboard, that may simply be "you steer and call, I plug."

At the dock, run a short drill: time how long it takes to find the kit, open a hatch, reach each seacock and close it, and push a plug into a through-hull (with the seacock closed or the boat hauled). You'll find seized seacocks, plugs that don't fit and floorboards that are screwed down. Fix those now.

Once a year, open the kit. Replace plugs that have dried and cracked, rescue tape that has gone gummy, putty past its date, and any tool that has rusted. Check flashlight batteries. Update your through-hull list if you added a transducer or new fitting.