520010-1 — Screw-in nylon drain
Nylon 1-inch drain body with a recess intended to retain installation sealant.
Sea-Dog Boat Drain Plugs: Garboard, Snap & T-Handle Guide
A boat's transom drain, bilge garboard outlet and removable drain plug can look similar but use different seals and attachment methods. Compare Sea-Dog's nylon drain fittings, bronze pipe-thread garboard drains, expanding snap- and T-handle plugs, and matching drain tubes by manufacturer part number before ordering.
Understand the four drain-part families
Threaded nylon drain
520010-1 uses a one-inch nylon drain body; its molded recess helps retain installation sealant. The 520021-1 kit replaces the plug and gasket only.
Bronze garboard fittings
520040-1 is the complete machined-bronze drain with a 1/2-inch NPT plug and two-inch mounting flange. Its matching replacement closure is 520041-1.
Removable compression plugs
For round openings, choose by measured size, handle and metal: snap-lever brass/stainless or T-handle brass/stainless. The 1-1/4-inch 520082-1 differs from the one-inch models.
Drain tubes are separate parts
520230-1 is a one-inch-diameter formed brass tube requiring flaring; 520320-1 is a white adjustable HDPE tube with a locking nut.
Sea-Dog boat drain plugs and tubes by MPN
The chart separates full fittings, replacement closures, removable plugs and installable tubes. Each link jumps to the exact store item farther down the page.
| Sea-Dog MPN | Part type | Manufacturer specification | Selection note |
|---|---|---|---|
| 520010-1 | Screw-in nylon drain | 1-inch drain body; nylon; sealant-recessed base | Nylon 1-inch drain body with a recess intended to retain installation sealant. |
| 520021-1 | Plug and gasket replacement | Replacement for 520010, 520020 and 520030 | Plug-and-gasket replacement for the three specified Sea-Dog drain bodies; not a complete drain. |
| 520040-1 | Bronze garboard drain | 1/2-inch NPT plug; 2-inch flange; #10 FH fasteners | Machined-bronze complete drain and square-head threaded closure for haul-out drainage. |
| 520041-1 | Bronze garboard replacement plug | Plug only for 520040; 1/2-inch NPT | Replacement square-head bronze plug intended specifically for the 520040 drain body. |
| 520050-1 | Nylon garboard drain | Integrated 1-1/8-inch tube; O-ring plug; #8 FH fasteners | UV-stabilized nylon garboard assembly with a built-in drain tube and O-ring closure. |
| 520070-1 | Brass snap-handle plug | 1-inch; brass and nitrile rubber | Cam-action one-inch expanding plug with a brass snap handle. |
| 520075-1 | Stainless snap-handle plug | 1-inch; stainless and nitrile rubber | Stainless steel and nitrile-rubber alternative to the one-inch brass snap-handle style. |
| 520080-1 | Brass T-handle plug | 1-inch; brass and nitrile rubber | One-inch brass T-handle plug; turn clockwise to secure and the reverse to release. |
| 520082-1 | Larger brass T-handle plug | 1-1/4-inch; brass and nitrile rubber | The 1-1/4-inch size of the brass T-handle family, not a substitute for a one-inch opening. |
| 520085-1 | Stainless T-handle plug | 1-inch; stainless and nitrile rubber | Stainless steel one-inch T-handle drain plug with a nitrile-rubber sealing element. |
| 520230-1 | Formed brass drain tube | 1-inch outer diameter; 2-7/8-inch length; flaring tool required | Formed-brass tube for a transom or well drain; installation requires flaring. |
| 520320-1 | Adjustable HDPE drain tube | 1-inch hole; 3/4–2-1/2-inch bulkhead; white HDPE | White adjustable tube with locking nut; designed for snap- and T-handle drain plugs. |
The manufacturer's one-inch measurements on expanding plugs do not identify a 1/2-inch NPT garboard thread. Confirm the original fitting, and follow the marine installation instructions for sealing and fastening.
How to choose a drain replacement
- Identify the drain's location and sealing design: screw-in nylon, bronze garboard or rubber expansion plug.
- Measure the existing opening and match any thread callout, including 1/2-inch NPT on the 520040 bronze garboard family.
- Check component scope and installation requirements. A plug-only item will not replace a damaged base, and 520230-1 brass drain tubing requires a flaring tool.
Sea-Dog drain plugs, garboard fittings and tubes
Choose from the specifically identified components below. Product photos link to their corresponding listings; check the number, materials and dimensions before ordering.
520021-1 — Plug and gasket replacement
Plug-and-gasket replacement for the three specified Sea-Dog drain bodies; not a complete drain.
520040-1 — Bronze garboard drain
Machined-bronze complete drain and square-head threaded closure for haul-out drainage.
520041-1 — Bronze garboard replacement plug
Replacement square-head bronze plug intended specifically for the 520040 drain body.
520050-1 — Nylon garboard drain
UV-stabilized nylon garboard assembly with a built-in drain tube and O-ring closure.
520070-1 — Brass snap-handle plug
Cam-action one-inch expanding plug with a brass snap handle.
520075-1 — Stainless snap-handle plug
Stainless steel and nitrile-rubber alternative to the one-inch brass snap-handle style.
520080-1 — Brass T-handle plug
One-inch brass T-handle plug; turn clockwise to secure and the reverse to release.
520082-1 — Larger brass T-handle plug
The 1-1/4-inch size of the brass T-handle family, not a substitute for a one-inch opening.
520085-1 — Stainless T-handle plug
Stainless steel one-inch T-handle drain plug with a nitrile-rubber sealing element.
520230-1 — Formed brass drain tube
Formed-brass tube for a transom or well drain; installation requires flaring.
520320-1 — Adjustable HDPE drain tube
White adjustable tube with locking nut; designed for snap- and T-handle drain plugs.
More boat hardware references
Moeller marine drain plug and tube sizing  •  Sea-Dog deck-fill caps, keys and emergency plugs
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