Bearing Assembly Tapered Roller – Fits Mercury Marine/Mercruiser Alpha One (Replaces Mercury Marine/Mercruiser 31-61100A1, Sierra 18-1165, Mallory 9-75117)
Bearing Assembly Tapered Roller – Fits Mercury Marine/Mercruiser Alpha One (Replaces Mercury Marine/Mercruiser 31-61100A1, Sierra 18-1165, Mallory 9-75117) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.
Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Bearing Assembly Tapered Roller – Fits Mercury Marine/Mercruiser Al...
Product Details
This high-quality Bearing Assembly Tapered Roller – Fits Mercury Marine/Mercruiser Alpha One is designed as a direct replacement for the upper bearing in various sterndrive models. It is engineered for a precise fit on Mercury Marine/Mercruiser Alpha One Gen II (1982–1995), Mercruiser Sterndrive Outdrives R-MR ALPHA ONE (1982–1995), and Mercruiser Sterndrive Transoms R-MR-Alpha One (1982–1995).
This assembly serves as a direct interchange for Mercury Marine/Mercruiser 31-61100A1, Sierra 18-1165, Mallory 9-75117, and GLM 21510.
- Replaces the upper bearing on specific Alpha One and R/MR sterndrives.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury Marine / Mercruiser | 31-61100A1 |
| Sierra | 18-1165 |
| Mallory | 9-75117 |
| GLM | 21510 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This bearing assembly fits a wide range of Mercury Marine/Mercruiser engines. Please verify your model and serial number range where applicable.
| Brand | Model | Years | OEM Part No. | Notes |
|---|---|---|---|---|
| Mercury Marine / Mercruiser | 225-S | 1974 | 31-61100A1 | |
| Mercury Marine / Mercruiser | 233 | 1975–1977 | 31-61100A1 | |
| Mercury Marine / Mercruiser | 470 | 1976–1977 | 31-61100A1 | |
| Mercury Marine / Mercruiser | 120/140 | 1978–1982 | 31-61100A1 | |
| Mercury Marine / Mercruiser | 165 | 1978–1981 | 31-61100A1 | |
| Mercury Marine / Mercruiser | 898 | 1978–1982 | 31-61100A1 | |
| Mercury Marine / Mercruiser | 260 | 1978–1982 | 31-61100A1 | |
| Mercury Marine / Mercruiser | 470 | 1978–1982 | 31-61100A1 | |
| Mercury Marine / Mercruiser | 485 | 1980–1982 | 31-61100A1 | |
| Mercury Marine / Mercruiser | 228 | 1978–1982 | 31-61100A1 | |
| Mercury Marine / Mercruiser | Alpha One SS | 1986–1989 | 31-61100A1 | |
| Mercury Marine / Mercruiser | Alpha One Gen II | 1991–1995 | 31-61100A1 | S/N 0D469859 THRU 0F679999 |
| Mercury Marine / Mercruiser | R/MR/Alpha One (Sterndrive) | 1983–1990 | 31-61100A1 | S/N 6225577 THRU 0F386995 |
| Mercury Marine / Mercruiser | R/MR/Alpha One (Transom Assembly) | 1983–1990 | 31-61100A1 | S/N 6216687 THRU 0F386995 |
| Mercury Marine / Mercruiser | SSM II/III/IV/V | 1982–1995 | 31-61100A1 |
Technical Specs
- Product Type
- Tapered Roller Bearing Set
- Weight
- 0.20 kg (0.44 lbs)
- Product Dimensions
- 7.13" L x 1.25" W x 6.0" H
- Warranty
- Limited Lifetime
- Made In
- Japan
- Application
- Replaces upper bearing on specific Alpha One and R/MR sterndrives.
What’s in the Box
- 1 x Tapered Roller Bearing Set
Installation Notes
- Disconnect the battery and ensure the engine is off and cool.
- Properly support the sterndrive unit before disassembly.
- Remove the upper gearcase housing cover to access the bearing assembly.
- Carefully extract the old bearing and race using appropriate puller tools.
- Clean the housing thoroughly, removing any debris or old grease.
- Press the new bearing race into the housing evenly.
- Pack the new tapered roller bearing with marine-grade grease.
- Install the new bearing into the race.
- Reassemble the upper gearcase, ensuring all seals and gaskets are correctly installed.
- Torque all fasteners to the manufacturer's specified values.
Troubleshooting & FAQ
What are the signs of a failing sterndrive bearing?
Common symptoms include a rumbling, grinding, or whining noise from the sterndrive, especially when turning or at speed. You might also notice excessive play or looseness in the propshaft.
Does this bearing fit my specific Alpha One model?
This assembly is designed for many R/MR, Alpha One, and Alpha One Gen II models from 1974–1995. Please check the compatibility table and verify your serial number to ensure a correct fit.
Is this bearing for the upper or lower unit?
This is an upper bearing assembly for the specified sterndrive models.
What is the recommended replacement interval?
Bearings do not have a fixed replacement schedule. They should be inspected for wear, noise, or damage during regular sterndrive service and replaced as needed.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). It is built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility and batch-inspected for consistency.
What are the shipping speed & cost?
We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
What is the warranty & returns policy?
This product is 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 if the part is unused and in its original condition. See our policy page or reach out for instructions.
Safety & Important Info
- Verify images and 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.
Payment & Security
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