Sea-Dog 520500-1
Nylon scupper flapper valve
A soft black flap helps limit backwash in a self-bailing cockpit. It is a valve component, not a standalone hose-tail thru-hull.
Identify Sea-Dog Scupper Valves & Marine Thru-Hull Drains
Boat drain outlets can have matching white flanges yet connect to different hose sizes. This Sea-Dog identification chart separates a surface scupper flapper from three threaded-body polypropylene thru-hull drains. Use the original part number and manufacturer drawing dimensions to match the fitting being replaced.
Recognize the drain hardware by type
A black flapper at the outlet
520500-1 is the scupper valve. It surface-mounts with four #6 flat-head fasteners and is a separate part from the complete 520510 scupper thru-hull.
Small white thru-hull
520750-1 uses a 3/4-inch hose. The Sea-Dog drawing lists flange A 1-13/16 inches and overall D 3-1/2 inches.
Intermediate white thru-hull
520770-1 is listed for 1-1/8 to 1-1/4-inch hose. Its flange A dimension is 2-3/16 inches.
Larger white thru-hull
520790-1 accepts 1-1/2-inch hose and has a 2-7/8-inch A dimension. Check mounting space as well as the hose connection.
Compare the Sea-Dog part markings
The A, B and D labels come from Sea-Dog's individual dimensioned product drawings. A describes the outward flange dimension for these products; verify the drawing before treating any measurement as a hole-cutout dimension.
| Sea-Dog MPN | Component | Hose size | Drawing dimension A | Drawing B or D |
|---|---|---|---|---|
| 520500-1 | Nylon scupper flapper valve | Not a hose fitting | A: 2-13/16 in | B: 1-7/8 in |
| 520750-1 | White polypropylene thru-hull | 3/4 in | A: 1-13/16 in | D: 3-1/2 in |
| 520770-1 | White polypropylene thru-hull | 1-1/8 to 1-1/4 in | A: 2-3/16 in | D: 3-9/16 in |
| 520790-1 | White polypropylene thru-hull | 1-1/2 in | A: 2-7/8 in | D: 4-3/16 in |
Above-waterline use
Sea-Dog lists these polypropylene thru-hulls for drainage above the water line, and the scupper flap for self-bailing cockpits. Do not use them in place of an approved below-waterline seacock or shutoff assembly. The 520500-1 flap is a standalone valve component and replacement part for 520510.
How to confirm the old outlet
- Identify whether the missing component is a surface scupper valve or a hose-connected thru-hull; these are not equivalent items.
- Measure the hose inside diameter. For the listed thru-hulls the Sea-Dog F dimension corresponds to 3/4, 1-1/8 to 1-1/4, or 1-1/2 inches.
- Compare the flange and overall body dimensions from the correct Sea-Dog model drawing, and check hull thickness before fitting.
- Use these molded thru-hulls only in approved above-waterline drainage locations; follow the boat manufacturer's requirements for below-waterline fittings.
Identify these exact Sea-Dog parts
These cards link to individually identified product listings. Open the matching part to check its current condition, contents and availability.
Sea-Dog 520750-1
White polypropylene thru-hull
Choose by the exact 3/4-inch hose connection and verify the hull opening and mounting thickness.
Sea-Dog 520770-1
White polypropylene thru-hull
This hose range is different from the smaller 520750 and the larger 520790.
Sea-Dog 520790-1
White polypropylene thru-hull
For a suitable 1-1/2-inch drain line above the waterline. Not a seacock or below-waterline shutoff.
Related parts identification
Sea-Dog boat drain plugs and garboard fittings • Sea-Dog marine tank vent identification
Visto recientemente
Inventario de piezas para vehículos recreativos nuevo y actualizado: consulte con frecuencia
Siempre estamos agregando piezas de RV nuevas y usadas a nuestro inventario, así que asegúrese de volver a consultarlo periódicamente.
Si no ve la pieza que necesita hoy, es posible que aún la tengamos en stock: nuestra base de datos interna incluye miles de piezas de vehículos recreativos nuevas que aún no están publicadas en línea.
Envíenos un mensaje de texto o correo electrónico con el número de producto o modelo y verificaremos la disponibilidad de inmediato.
Nuestros productos