520010-1 — Screw-in nylon drain
Look for the one-inch nylon mounting body and the recess formed into its base.
Identify Sea-Dog Boat Drain Plugs by Part Number & Handle
Matching a replacement drain plug on a boat starts with its opening, not its colour. Sea-Dog supplies threaded drains, bronze and nylon garboard fittings, lever-lock and T-handle plugs, and drain tubes. Their part numbers identify different sealing mechanisms. Use this chart to inspect a removed part and narrow down the correct replacement.
Which drain component is on your boat?
Is the drain body staying in place?
If only a removable closure is missing, identify its original housing. Sea-Dog 520021-1 services 520010, 520020 and 520030; 520041-1 belongs to the bronze 520040.
Is the fitting threaded or expanding?
The square-top 520040 garboard plug seals on 1/2-inch NPT tapered threads. Snap-handle and T-handle models compress a rubber seal in a round opening.
Measure the actual opening
One-inch and 1-1/4-inch expanding plugs are separate sizes. Compare the bore and original plug, not just the handle style.
Inspect the drain tube
520230-1 is a formed brass tube that requires flaring. White HDPE 520320-1 has a locking nut and adjusts to 3/4–2-1/2-inch bulkheads.
Sea-Dog 520-series identification table
Use the original drain body's markings wherever possible; the dimensions below describe the specified Sea-Dog component, not universal boat compatibility.
| Part number | What to identify | Size / construction | Replacement clue |
|---|---|---|---|
| 520010-1 | Screw-in nylon drain | 1-inch drain body; nylon; sealant-recessed base | Look for the one-inch nylon mounting body and the recess formed into its base. |
| 520021-1 | Plug and gasket replacement | Replacement for 520010, 520020 and 520030 | Services a matching 520010, 520020 or 520030 housing without changing the base. |
| 520040-1 | Bronze garboard drain | 1/2-inch NPT plug; 2-inch flange; #10 FH fasteners | Identify the two-inch bronze flange and 1/2-inch tapered pipe-thread plug. |
| 520041-1 | Bronze garboard replacement plug | Plug only for 520040; 1/2-inch NPT | Match the original 520040 garboard fitting before ordering this plug-only repair. |
| 520050-1 | Nylon garboard drain | Integrated 1-1/8-inch tube; O-ring plug; #8 FH fasteners | Different from the bronze NPT fitting: this nylon design has an integrated 1-1/8-inch tube. |
| 520070-1 | Brass snap-handle plug | 1-inch; brass and nitrile rubber | The brass handle folds down to lock the cam seal after tightening. |
| 520075-1 | Stainless snap-handle plug | 1-inch; stainless and nitrile rubber | One-inch snap-lever design with stainless hardware rather than brass. |
| 520080-1 | Brass T-handle plug | 1-inch; brass and nitrile rubber | A threaded T-shaped grip operates the brass-and-rubber expanding seal. |
| 520082-1 | Larger brass T-handle plug | 1-1/4-inch; brass and nitrile rubber | Compare the 1-1/4-inch size against 520080-1 before selecting a larger plug. |
| 520085-1 | Stainless T-handle plug | 1-inch; stainless and nitrile rubber | A one-inch T-handle model using stainless hardware and rubber instead of brass. |
| 520230-1 | Formed brass drain tube | 1-inch outer diameter; 2-7/8-inch length; flaring tool required | Check the 2-7/8-inch brass tube length and flaring-tool requirement. |
| 520320-1 | Adjustable HDPE drain tube | 1-inch hole; 3/4–2-1/2-inch bulkhead; white HDPE | White HDPE tube for a one-inch hole, adjustable across 3/4–2-1/2-inch wall thickness. |
A plug that looks close may still leak if its rubber expansion range, thread or mating drain body differs. Keep the old part available for comparison.
Three checks before selecting a replacement
- Look for a part number on the plug or drain housing. If none is present, record whether it threads in, snaps down or tightens with a T-handle.
- Measure the hole or pipe thread and inspect the body for a flat flange, square wrenching head, rubber expanding seal or integrated O-ring.
- Check whether you need an entire fitting, a plug-and-gasket kit or a separate drain tube. Confirm material and attachment method before replacing.
Find the exact Sea-Dog drain parts
These products are listed by their individual manufacturer numbers. Open an item to check its listing details and current availability.
520021-1 — Plug and gasket replacement
Services a matching 520010, 520020 or 520030 housing without changing the base.
520040-1 — Bronze garboard drain
Identify the two-inch bronze flange and 1/2-inch tapered pipe-thread plug.
520041-1 — Bronze garboard replacement plug
Match the original 520040 garboard fitting before ordering this plug-only repair.
520050-1 — Nylon garboard drain
Different from the bronze NPT fitting: this nylon design has an integrated 1-1/8-inch tube.
520070-1 — Brass snap-handle plug
The brass handle folds down to lock the cam seal after tightening.
520075-1 — Stainless snap-handle plug
One-inch snap-lever design with stainless hardware rather than brass.
520080-1 — Brass T-handle plug
A threaded T-shaped grip operates the brass-and-rubber expanding seal.
520082-1 — Larger brass T-handle plug
Compare the 1-1/4-inch size against 520080-1 before selecting a larger plug.
520085-1 — Stainless T-handle plug
A one-inch T-handle model using stainless hardware and rubber instead of brass.
520230-1 — Formed brass drain tube
Check the 2-7/8-inch brass tube length and flaring-tool requirement.
520320-1 — Adjustable HDPE drain tube
White HDPE tube for a one-inch hole, adjustable across 3/4–2-1/2-inch wall thickness.
Related marine parts identification
Moeller drain plugs and flanged tubes • Sea-Dog deck-fill cap and key identification
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