Mercury Gearcase Driveshaft Oil Seal 26-413651
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Mercury Gearcase Driveshaft Oil Seal 26-413651
Part Number: 26-413651 (short ref: 413651)
Brand: Mercury / Quicksilver
Product Type: Gearcase Driveshaft Oil Seal (OEM)
System: Outboard Lower Unit / Gearcase
Position: Driveshaft / water-pump base area
Supersedes: 41365 / 26-41365
Quantity Required: 2 per assembly
GTIN / UPC: 745061144828
Approximate Weight: 15 g each / ~30 g per pair
What This Part Does
The 26-413651 is a genuine OEM oil seal that sits beneath the water-pump base in the gearcase of selected small Mercury outboard engines. Two seals are used per assembly, stacked at the driveshaft location to seal gearcase lubricant away from the water-pump cavity. Correct quantity and installation orientation are both critical during service.
Compatible Applications
Confirm your engine horsepower, serial number, gearcase design, and driveshaft housing diagram before ordering. Mercury used multiple lower-unit designs within the same horsepower ranges — do not select this seal by appearance alone.
- Mercury 6 HP outboard
- Mercury 8 HP outboard
- Mercury 9.9 HP outboard
- Mercury XR10
- Mercury 10 MAGNUM
- Mercury 10 MARATHON
- Mercury 10 SEA PRO
- Mercury 15 HP outboard
Mercury references show 41365 / 413651 across multiple serial ranges within these engine families. Always verify by serial number and gear-housing diagram.
Serial Number Notice
Several oil seals and water-tube seals are used in the same lower-unit assembly — do not order by physical appearance or size alone. Match by part number and confirm against the gearcase diagram for your specific engine serial number.
When to Replace
- Gearcase oil shows signs of water contamination (milky or foamy appearance)
- Oil leakage visible around the driveshaft or water-pump base area
- Seal lip is worn, hardened, cracked, or damaged on inspection
- Water-pump base is removed during lower-unit service (replace as a matter of course)
- Driveshaft sealing surface shows evidence of leakage or seal wear
Installation Notes
- Quantity: 2 seals required per assembly — always replace both at the same time
- Install both seals in the correct orientation per the Mercury service manual for your engine
- While the assembly is apart, inspect the water-pump base, driveshaft sealing surface, water-pump base gasket, quad ring, and water-tube seal
- Inspect the water-pump base gasket and related sealing components before reassembly
- Recheck gearcase oil level after reassembly and run the engine to confirm no leaks
Part Number Cross-Reference
- Current OEM: 26-413651
- Short Reference: 413651
- Supersedes: 41365 / 26-41365
- Aftermarket cross-reference: Sierra 18-0581 (third-party reference only)
Parts Desk Insights
Best use case: Order 26-413651 whenever the water-pump base is coming off a 6–15 HP Mercury outboard lower unit — it’s a low-cost seal that’s already exposed at that point. Replacing both seals during any lower-unit service is strongly recommended, since the second seal is in the same location and requires the same disassembly to reach.
Common issues: The most frequent mistake is ordering only one seal when two are required at this location. A second common issue is confusing this driveshaft oil seal with the water-tube seal or other seals in the same lower-unit assembly — always match by part number, not by appearance or general seal size.
Related Parts
- Mercury Quicksilver 192043 Water Pump Base Gasket — 6–15 HP Outboard
- Mercury Quicksilver 19202001 Water Pump Plate Gasket — 6 / 8 / 9.9 HP Outboard
- Mercury Mariner Lower Unit Gear Housing Seal Kit 26-43035A4
- Mercury Mariner Upper Driveshaft Oil Seal 26-43035
- Mercury Mariner Driveshaft Lower Unit Oil Seal 26-43036
- Mercury Water Pump Base to Face Plate Gasket 27-39625
- Mercury Outboard Water Pump Impeller 8-Blade 8M0135803
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
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