










It’s the upper crankshaft oil seal for Mercury / Mariner outboard / stern drive engines (“Seal, Upper”).
Mercury‑Marine identifier: part number 26‑817397‑1 (sometimes written without the hyphen or with the trailing digit “1”: 26‑8173971).
The seal is used on Mercury / Mariner 60 hp Bigfoot motor(s) as one listing shows.
The “upper seal” suggests its position is at or toward the top of the engine’s crankcase / housing — often sealing around the crankshaft as it exits the upper housing. That helps keep oil in where it belongs, preventing leaks.
The part is labeled as the Upper Crankshaft Oil Seal (aka “Seal, Upper”).
NSN (National Stock Number) for it is 5330‑01‑518‑5579 (which corresponds to 26‑817397‑1).
The brand “Quicksilver” (Mercury’s OEM brand spare) also lists this seal under part number 26‑8173971.
It is an OEM genuine Mercury/Mariner part.
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| Brand | Unbranded |
|---|---|
| Manufacturer Part Number | 26-817397-1 |
| Unit Quantity | 1SET=2PCS |
| Country/Region of Manufacture | Taiwan |
| Type | Upper crankshaft oil seal |
| Engine Type | Mercury / Mariner outboard / stern drive engines |
| Mercury‑Marine identifier: | 26‑817397‑1 |
| Fits | Mercury / Mariner 60 hp Bigfoot motor(s) |

