How to Inspect and Clear Cockpit Scuppers and Deck Drains

Start in the cockpit and on deck. Find each drain grate, gutter and scupper, then go below or open the hatches and follow its hose to where it leaves the boat. Write down which ones exit above the waterline and which exit below, and which have seacocks. If any drain hose ends in the bilge instead of going overboard, note it: BoatUS calls deck drains that empty into the bilge a recipe for disaster, because the boat then depends on the bilge pump and battery to stay afloat.

With the boat floating at its normal load, look at the transom. How far above the waterline are the scupper openings? BoatUS says cockpit decks are meant to sit a minimum of four inches above the waterline but many don't, and that a repower with a heavier four-stroke, a loaded fish box, an anchor and chain in the stern or a few coolers can push scuppers to or below the waterline. A boat with floating-ball scuppers added to stop back-flooding is a warning sign that its scuppers are too low. If yours are close to the water, keep heavy gear forward and talk to a surveyor.

Lift or unscrew the grates and pull out leaves, sand, fishing line, bait scraps and bottle caps. Flush each drain with a garden hose. If water backs up, push a flexible plastic snake or stiff tubing down the hose gently. Skip screwdrivers and coat hangers: they can puncture a hose you can't see.

From outside the hull, look at each scupper outlet. A flapper should be soft, lie flat and swing open easily. Replace it if it's torn, hard, curled or crusted with growth that holds it open. Pour water into the drain and make sure it opens and lets the water out. Aftermarket one-way scuppers come in three main styles, BoatUS notes: duckbill, flapper and ball. Many ball-style units twist or unscrew from their base so you can clear leaves trapped behind the ball; whatever the style, check it regularly for debris that holds it open. If you swap a worn scupper valve for a new one, bed it with marine sealant and use the maker's fasteners and instructions. Remember what BoatUS points out: ball-style and flapper scuppers help with back-splash, but they are not designed to keep a boat afloat.

Follow each hose with a flashlight and squeeze it along its length. Look for cracks, a brittle or chalky feel, soft spots, kinks and low sags that hold water and dirt. BoatUS says thin corrugated plastic hose is a poor choice for scupper drains and has no place below the waterline, and that many hoses on aging boats are well past their design life. Replace bad hose with reinforced hose of the type and size your builder specifies.

In BoatUS's sinking files, the cockpit-drain problems were missing hose clamps, broken drain fittings, broken through-hulls and loose hoses, and on some small powerboats a hose was never connected to the drain at the factory. Make sure every hose is pushed fully onto its fitting and held with tight, all-stainless clamps with no rust. Where the hose barb is long enough, BoatUS recommends two clamps with the screws on opposite sides; if it's too short for two, use one good clamp rather than a second one that cuts the hose.

If a drain exits below the waterline, its seacock should open and close smoothly through its full travel; BoatUS suggests exercising seacocks monthly. Look for weeping, green or pink corrosion and a handle blocked by gear. Many cockpit drain seacocks are meant to stay open so rain can drain; follow your builder's guidance, and make sure the hose and clamps are sound so leaving it open is safe.

Close any hatches, then flood the cockpit with a garden hose or a few buckets of water. BoatUS recommends exactly this: inundate the suspect areas and see where the water goes. Time how long the cockpit takes to drain, then go below with a flashlight and look at every drain hose, fitting and the bilge for new water. Do the same for the deck gutters, the anchor locker and the engine well. If the bilge still fills after rain and the drains test fine, keep hosing one area at a time: rub rail joints, deck hardware and rail bases, windshield seals, engine-bay vents and the anchor locker drain hose all let rain in on older boats. A slow drain usually means a partial clog; water in the bilge means a leak you need to find.

BoatUS blamed most of those dockside rain sinkings on hatches that weren't gasketed, weren't sealed or weren't dogged down, often hatches right in front of the outboard well. Check that every deck hatch and inspection port has a gasket that isn't flattened or torn, that its gutter drain is clear, and that it latches tight. Dog them down every time you leave the boat. Screw-in inspection ports count too: the BoatUS Foundation describes a boat whose motor-well access port had been opened and never resealed, so rain trickled into the bilge until it overwhelmed the pump.

If you can't see a drain hose or its through-hull, you can't know it's failing. BoatUS suggests creating access where needed and covering the opening with a watertight deck hatch or inspection port. Get help with this if it means cutting into a deck or liner.

Before you leave the boat, clear the drains, dog the hatches, and make sure the bilge pump works and its battery is charged. If you use a cover, make sure it can't sag and hold a pool of rain: BoatUS describes a boat whose cover filled with rainwater until it sank. Keep weight out of the stern: move heavy gear forward and pump out livewells and fish boxes, which BoatUS also lists as contributors.

Ice and snow can block scuppers and drains just like leaves, and a frozen flapper can stick shut. Water trapped in a sagging drain hose can freeze and crack it, and you won't see the leak until it thaws. On a boat with a cabin, BoatUS warns that a cockpit drain clogged with leaves or ice can back water up and into the cabin, which is how winter mold problems start; and fittings that never leak can drip for days while heavy snow slowly melts, so look below after a big snowfall. If the boat stays in the water over winter, clear snow and ice from the cockpit and drains after every storm. If it's stored ashore, BoatUS suggests leaving the cockpit drain seacock open so rain and meltwater can drain, and visiting every few weeks to be sure drains haven't clogged. A well-supported winter cover keeps most of the snow out of the cockpit to begin with.