Attwood Marine Stainless Steel Scupper Valve, SS316, Neoprene Flap, Mirror Finish

Overview

The Attwood Marine Stainless Steel Scupper Valves is a range of barbed stainless steel scupper valves for cockpit, deck, and transom drain installations above the water line. These fittings combine a polished stainless exterior with an internal scupper flap that helps limit backwash when water pushes back toward the drain outlet.

This range covers 1-1/2 in and 2 in hose sizes, giving boat builders and owners a straightforward way to match the valve to existing drain hose and hull thickness. The bodies use Enhanced 316 stainless steel alloy, and the barbed tail gives room for hose clamps at the connection point.

Key features

• Enhanced 316 stainless steel alloy body for drain outlets exposed to spray, washdowns, and saltwater air.
• Scupper flap uses tough neoprene rubber with a molded V that seats into the grooved body to help reduce backwash.
• Concealed, corrosion-proof fasteners keep the outside face clean and reduce exposed hardware around the drain outlet.
• Barbed tail end leaves room for multiple hose clamps, which is useful where drain hose movement and vibration need a secure connection.
• Channel under the flange helps hold a bead of sealant during installation for a cleaner seal at the hull or transom surface.
• Wrench flats or an end notch give the installer a gripping surface so the fitting can be tightened from inside the hull.
• Intended for installation above the water line only.

Variants

This product is offered in two hose-size configurations for matching different scupper drain runs.

The hose size, thread size, installation hole saw size, and maximum hull thickness change between the two variants. The scupper flap construction, stainless steel valve body, and above-waterline installation requirement remain consistent across these barbed scupper valve models.

• 66553-1: 1-1/2 in hose size. This version uses 1-1/2 in NPSM threads, a 2 in installation hole saw size, and supports up to 3 in maximum hull thickness.
• 66555-1: 2 in hose size. This version uses 2 in NPSM threads, a 2-1/2 in installation hole saw size, and supports up to 2 in maximum hull thickness.

Installation and fit

Match the valve to the inside diameter of the drain hose already on the boat, then confirm the hole saw size and available hull thickness before cutting or replacing an existing fitting. The 1-1/2 in version has a 3 in flange outside diameter and 5-1/2 in total length, while the 2 in version has a 3-5/8 in flange outside diameter and 4-1/2 in total length.

Because this is a scupper valve, placement matters. It belongs in an above-waterline drain outlet where the flap can help with backwash while still allowing deck or cockpit water to leave the boat. The barbed outlet should be paired with hose of the correct size and clamps suitable for the hose and installation environment.

Use on board

These valves are a good match for owners, yards, and builders working on cockpit drains, deck drains, and transom scupper outlets where a stainless exterior is preferred over plastic. They make sense on fishing boats, center consoles, cruisers, and other vessels where drain outlets see spray, sun, and regular washdowns.

Maintenance and care

Rinse the exterior with fresh water after saltwater use and inspect the flap during routine cleaning. A flap that is blocked by debris, marine growth, or hardened residue may not seat cleanly, so keeping the scupper area clear helps the valve drain properly and limit backwash as intended.