Oil Seal – Fits Mercury Mariner 8HP 9.9HP 15HP 4-Stroke (Replaces 26-413651, 18-0581)
Oil Seal – Fits Mercury Mariner 8HP 9.9HP 15HP 4-Stroke (Replaces 26-413651, 18-0581) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
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Oil Seal – Fits Mercury Mariner 8HP 9.9HP 15HP 4-Stroke (Replaces 2...
Oil Seal – Fits Mercury Mariner 8HP 9.9HP 15HP 4-Stroke (Replaces 26-413651, 18-0581) is backordered and will ship as soon as it is back in stock.
Product Details
This Oil Seal – Fits Mercury Mariner 8HP 9.9HP 15HP 4-Stroke is designed for Mercury Mariner Quicksilver Marine 8hp, 9.9hp, and 15hp (323 cc) 4-Stroke outboard motors. Engineered as a direct-fit replacement for the lower gearcase unit, it ensures reliable sealing and protection for your outboard's critical components.
This seal replaces Mercury Marine OEM part numbers 26-413651 and 18-0581, providing a cost-effective aftermarket solution.
- Precision-fit for Mercury Mariner 8/9.9/15 HP 4-Stroke (323 cc) engines
- Suitable for lower gearcase applications
- Direct interchange for 26-413651 and 18-0581
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury Marine | 26-413651 |
| Mercury Marine | 18-0581 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
| Brand | Model | Rated HP | Stroke | OEM Part No. |
|---|---|---|---|---|
| Mercury Mariner Quicksilver Marine | 8/9.9/15 HP (323 cc) | 8, 9.9, 15 | 4-Stroke | 26-413651, 18-0581 |
Technical Specs
- Part Type
- Oil Seal
- Application
- Lower Gearcase Unit
- Compatible Engine Displacement
- 323 cc
- Stroke Type
- 4-Stroke
- Compatible HP Range
- 8, 9.9, 15 HP
What's in the Box
- 1 × Oil Seal
Installation Notes
- Disconnect the fuel line and ensure the engine is completely off before beginning work.
- Remove the lower gearcase unit from the outboard motor following the manufacturer's service manual.
- Carefully extract the old oil seal using an appropriate seal puller or pick tool, avoiding damage to the housing.
- Clean the seal bore thoroughly to remove any debris, corrosion, or old sealant residue.
- Lightly lubricate the new seal lip with marine-grade grease or gearcase oil.
- Install the new seal squarely into the bore using a seal driver or appropriately sized socket.
- Tap evenly around the seal perimeter until it seats fully and flush with the housing surface.
- Reassemble the lower gearcase unit, refill with the correct gear oil, and check for leaks after initial operation.
Troubleshooting & FAQ
How do I know if my oil seal needs replacement?
Signs include visible oil leaks around the lower gearcase, low gear oil levels, or milky/contaminated oil indicating water intrusion. Replace the seal if you notice any of these symptoms.
Is this seal compatible with all 8–15 HP Mercury engines?
No. This seal is designed exclusively for Mercury Mariner 8hp, 9.9hp, and 15hp 4-Stroke (323 cc) models. Always verify your engine's part number against 26-413651 or 18-0581 before purchase.
Can I reuse the old seal during reassembly?
No. Oil seals are single-use components. Reusing a seal can lead to improper seating, leaks, and potential damage to the gearcase.
Do I need any special tools to install this seal?
A seal driver or appropriately sized socket is recommended to ensure even installation. A seal puller or pick tool is helpful for removing the old seal without damaging the housing.
What type of lubricant should I use on the seal?
Use marine-grade grease or the same gear oil specified for your lower unit. Avoid petroleum-based lubricants that may degrade the seal material.
How often should this seal be replaced?
Replace the seal whenever you service the lower gearcase, notice leaks, or during routine maintenance intervals recommended in your engine's service manual—typically every 2–3 years or 100 hours of operation.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications against your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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