Bearing Cage Assembly – Fits Mercury/Mercruiser 15-25 HP Outboards (31-879877A1)
Bearing Cage Assembly – Fits Mercury/Mercruiser 15-25 HP Outboards (31-879877A1) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Bearing Cage Assembly – Fits Mercury/Mercruiser 15-25 HP Outboards ...
Product Details
This Bearing Cage Assembly is a crucial component designed for various Mercury Marine 2-stroke outboards from 15 to 25 HP. It fits a wide range of models, including the Marathon, Sea Pro, and Super 15 series, covering serial numbers from 0P017000 through 1B000001 and up. This roller bearing assembly ensures smooth operation within the engine's lower unit.
It serves as a direct replacement for Mercury part numbers 31-91866A1, 31-41620A1, and 31-879877A1, offering a reliable interchange for maintenance and repairs.
- Installation is specific to the engine model and requires appropriate tools.
- This is an OEM Mercury Marine part, ensuring factory-grade fit and function.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Superseded By | Notes |
|---|---|---|---|
| Mercury | 31-91866A1 | 31-879877A1 | |
| Mercury | 31-41620A1 | 31-879877A1 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This part is designed exclusively for Mercury Marine engines. Please verify your model and serial number range for an exact match.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 15 MARATHON XD | 15 | 2-Stroke | 0P017000-0P325499 | 31-879877A1 | Supersedes: 31-91866A1, 31-41620A1 |
| Mercury | 15 SEA PRO (XD) | 15 | 2-Stroke | 0P017000-0P325499 | 31-879877A1 | Supersedes: 31-91866A1, 31-41620A1 |
| Mercury | 20 (2 CYL.) | 20 | 2-Stroke | 0G760300-0T979999 | 31-879877A1 | Supersedes: 31-91866A1, 31-41620A1 |
| Mercury | 20 (2 CYL.) | 20 | 2-Stroke | 0P017000-0P325499 | 31-879877A1 | Supersedes: 31-91866A1, 31-41620A1 |
| Mercury | 20 (2 CYL.) | 20 | 2-Stroke | 0P325500 & Up | 31-879877A1 | Supersedes: 31-91866A1, 31-41620A1 |
| Mercury | 20 JET | 20 | 2-Stroke | 0G760300-0T979999 | 31-879877A1 | Supersedes: 31-91866A1, 31-41620A1 |
| Mercury | 20 JET | 20 | 2-Stroke | 0P017000-0P325499 | 31-879877A1 | Supersedes: 31-91866A1, 31-41620A1 |
| Mercury | 20 JET | 20 | 2-Stroke | 0T980000-0T999999 | 31-879877A1 | Supersedes: 31-91866A1, 31-41620A1 |
| Mercury | 20 JET | 20 | 2-Stroke | 1B000001 & Up | 31-879877A1 | Supersedes: 31-91866A1, 31-41620A1 |
| Mercury | 25 (2 CYL.) | 25 | 2-Stroke | 0T980000-0T999999 | 31-879877A1 | Supersedes: 31-91866A1, 31-41620A1 |
| Mercury | 25 (2 CYL.) | 25 | 2-Stroke | 1B000001 & Up | 31-879877A1 | Supersedes: 31-91866A1, 31-41620A1 |
| Mercury | 25 (2 CYL.) | 25 | 2-Stroke | 0P325500 & Up | 31-879877A1 | Supersedes: 31-91866A1, 31-41620A1 |
| Mercury | 25, 25 MARATHON, SUPER 15 (2 CYL.) | 25 | 2-Stroke | 0G760300-0T979999 | 31-879877A1 | Supersedes: 31-91866A1, 31-41620A1 |
| Mercury | 25, 25 MARATHON, SUPER 15 (2 CYL.) | 25 | 2-Stroke | 0P017000-0P325499 | 31-879877A1 | Supersedes: 31-91866A1, 31-41620A1 |
| Mercury | 25, 25 SEA PRO, SUPER 15 (2 CYL.) | 25 | 2-Stroke | 0G760300-0T979999 | 31-879877A1 | Supersedes: 31-91866A1, 31-41620A1 |
| Mercury | 25, 25 SEA PRO, SUPER 15 (2 CYL.) | 25 | 2-Stroke | 0P017000-0P325499 | 31-879877A1 | Supersedes: 31-91866A1, 31-41620A1 |
Technical Specs
- Product Type
- Bearing Assembly (Roller)
- Installation
- Engine-specific
- Weight
- 0.027 kg (0.06 lb)
- Dimensions
- 38.1 × 38.1 × 25.4 mm (1.50 × 1.50 × 1.00 in)
- Warranty
- None (OEM Mercury part)
- Other Technical Attributes
- OEM Mercury Marine part
What’s in the Box
- 1 x BEARING CAGE ASSY (31-879877A1)
Installation Notes
- Ensure the engine is off, in neutral, and the battery is disconnected before starting work.
- Access the lower unit or driveshaft housing according to your engine's service manual to locate the existing bearing.
- Carefully extract the old bearing cage assembly, taking care not to damage the housing. Note its orientation.
- Thoroughly clean the mounting surface of any old grease, dirt, or signs of corrosion.
- Apply a thin coat of marine-grade bearing grease to the new assembly and its seating area.
- Press the new bearing cage firmly and evenly into place until it is fully seated. Confirm it is correctly aligned.
- Reassemble the lower unit components in the reverse order of disassembly, torquing fasteners to manufacturer specifications.
Troubleshooting & FAQ
How do I confirm this bearing cage fits my specific outboard?
Verify your engine's model, year, and serial number against the detailed compatibility table provided on this page. Your model and serial number range must be listed for this part to fit correctly.
What are the signs of a failed bearing cage assembly?
Common symptoms include a grinding or rumbling noise from the lower unit, excessive vibration during operation, or the presence of metal shavings in the gear lube upon inspection.
Is a special type of grease required for installation?
Yes, it is essential to use a high-quality marine-grade grease specifically formulated for bearings and lower unit applications. This ensures proper lubrication, corrosion protection, and longevity.
Why should I replace the entire assembly instead of just the internal rollers?
This component is sold as a complete, pre-assembled unit to guarantee correct tolerances, alignment, and performance. Attempting to rebuild it with separate rollers is not recommended and can lead to premature failure.
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 vs 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.
Payment & Security
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