A missing or damaged Sea-Dog deck-fill cap is easier to identify once you separate the fill body, replacement cap, operating key and emergency plug. The numbers in this reference describe different parts. Measure the existing opening and read its fuel or water marking before choosing a replacement.
Distinguish the fill from its service parts
351320-1 is a gas-marked stainless hose deck fill from Sea-Dog's earlier catalog. It joins a 1½-inch hose; it is not just the top cap.
351390-1 is the threaded slotted cap and chain for 1½-inch Sea-Dog hose fills. The 351399-1 stainless and 357399-1 nylon items are separate keys.
357390-1 is a nitrile/Buna rubber emergency plug. It is not a substitute for installing a correct, serviceable deck-fill cap permanently.
Sea-Dog deck-fill MPN identification
The hose size in the chart applies to the fill body, not to the overall diameter of the cap.
| MPN | Component | Material | Purpose | Identifying fit |
|---|---|---|---|---|
| 351320-1 | Gas hose deck fill | 316 stainless steel | Complete fill assembly | Gas marking; 1½-in hose |
| 351390-1 | Slotted cap and chain | 316 stainless steel | Replacement cap | Sea-Dog 351320–351323 hose fills |
| 351399-1 | Stainless deck-fill key | 316 stainless steel | Opening slotted caps | 1 3/16-in centre-to-centre holes |
| 357390-1 | Emergency deck-fill plug | Nitrile/Buna rubber | Temporary emergency plug | Check exact fill opening |
| 357399-1 | Nylon deck-fill key | Black nylon | Opening slotted caps | Multi-spacing key; verify cap |
351320-1 is documented in Sea-Dog's earlier catalog; newer manufacturer tables show other variants. Confirm the body marking and exact part before ordering. The nylon key's individual pin spacings should be checked against the actual cap.
Inspect the original cap and fill opening
Read the GAS, WATER, DIESEL or WASTE marking on the existing body, inspect the cap threads and seal, and compare the attachment chain and opening size. A replacement key cannot correct damaged threads or an incorrect cap.
Sea-Dog's 351390-1 cap belongs to the 351320–351323 hose-fill family. Its 12 NPSM straight thread is not the same as the larger pipe-type or two-inch hose-fill cap systems. Always confirm the exact fitting family and closure.
Do not use the emergency plug as a permanent repair. Follow the vessel manufacturer's safety procedures when working with fuel or waste connections.
Find the matching Sea-Dog replacement part
Open each exact MPN for its listing and current availability.
Sea-Dog 351320-1
Earlier-catalog gas-marked fill body for 1½-inch hose, not a loose replacement cap.
Check exact listing and availability
Sea-Dog 351390-1
Replacement closure; check the exact 1½-inch hose-fill series.
Check exact listing and availability
Sea-Dog 351399-1
Cast stainless key for Sea-Dog stainless fill caps with matching hole spacing.
Check exact listing and availability
Sea-Dog 357390-1
Emergency-use plug; do not treat it as a permanent cap replacement without the correct application.
Check exact listing and availability
Sea-Dog 357399-1
Lightweight nylon key for compatible slotted deck-fill caps; match the pin spacing.
Check exact listing and availabilityRelated Sea-Dog hardware identification
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