Shim Kit – Fits Mercruiser Stern Drives C.R. (Replaces 15-31535A1)
Shim Kit – Fits Mercruiser Stern Drives C.R. (Replaces 15-31535A1) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Shim Kit – Fits Mercruiser Stern Drives C.R. (Replaces 15-31535A1)
Product Details
This aftermarket Shim Kit – Fits Mercruiser Stern Drives C.R. (Replaces 15-31535A1) is designed for a wide range of Mercruiser stern drive engines manufactured between 1962 and 1977. Compatible models include the 120/140, 160, 165, 225-S, 233, 250, 470, 888, and 898/228 series, as well as select Mercury Racing outboards.
This kit serves as a direct replacement for Mercury/Mercruiser part number 15-31535A1 and SEI part number 98-108-06K, ensuring precise fitment and function for maintenance or repair.
- Installation Location: Mounts between the bearing carrier and the gear housing.
- Built for Marine Use: All components are rated for demanding marine environments.
- Precise Adjustments: Includes multiple shim thicknesses required for adjusting bearing preload and gear backlash.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury/Mercruiser | 15-31535A1 |
| SEI | 98-108-06K |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This kit is verified for numerous Mercruiser stern drives, Alpha One Gen II counter-rotation models, and specific Mercury Racing/Mariner outboards as detailed in the compatibility chart.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercruiser | 120/140 | 120-140 | 4-Stroke | 1967–1969 | 15-31535A1 | Serial: 2062141-2791956 |
| Mercruiser | 120/140 | 120-140 | 4-Stroke | 1970–1977 | 15-31535A1 | Serial: 2791957-4893634 |
| Mercruiser | 160 | 160 | 4-Stroke | 1967–1969 | 15-31535A1 | Serial: 2065190-2763441 |
| Mercruiser | 165 | 165 | 4-Stroke | 1970–1977 | 15-31535A1 | Serial: 2763442-4890459 |
| Mercruiser | 225-S | 225 | 4-Stroke | 1974 | 15-31535A1 | Serial: 3856268-4200499 |
| Mercruiser | 233 | 233 | 4-Stroke | 1975–1977 | 15-31535A1 | Serial: 4200500 and up |
| Mercruiser | 250 | 250 | 4-Stroke | 1977 | 15-31535A1 | Serial: 4791300-4898729 |
| Mercruiser | 470 | 170 | 4-Stroke | 1976–1977 | 15-31535A1 | Serial: 4208730-4893934 |
| Mercruiser | 888 | 188 | 4-Stroke | 1971–1977 | 15-31535A1 | Serial: 3106717 and up |
| Mercruiser | 898/228 | 228 | 4-Stroke | 1977 | 15-31535A1 | Serial: 4782330-4898729 |
| Mercruiser | IA/IB/IC (EZ-SHIFT) | 4-Stroke | 1965–1966 | 15-31535A1 | Serial: 1776349-2065189 | |
| Mercruiser | IA/IB/IC | 4-Stroke | 1964 | 15-31535A1 | Serial: 1684188-1777798 | |
| Mercruiser | II (1.78:1) | 4-Stroke | 1968–1969 | 15-31535A1 | Serial: 2398798-2671321 | |
| Mercruiser | II | 4-Stroke | 1962–1963 | 15-31535A1 | Serial: 1474909-1602185 | |
| Mercruiser | II | 4-Stroke | 1964–1967 | 15-31535A1 | Serial: 1602186-2278488 | |
| Mercury Racing | MERC MOD-VP | 15-31535A1 | Serial: 83B807 and up | |||
| Mercury/Mariner | 2.4L (EFI) | 15-31535A1 | Serial: 0A168043 and below | |||
| Mercury/Mariner | 2.4L (EFI) | 15-31535A1 | Serial: 0A168044-0B290009 | |||
| Mercruiser | Alpha One Generation II Counter Rotation | 1991+ | 31535A1 | Fits SEI Marine Products part 98-108-06K |
Technical Specs
- Product Type
- Shim Kit
- Installation
- Bearing Carrier to Gear Housing
- Housing Material
- Metal (likely steel)
- Working Pressure
- Marine environment rated
- Product Height
- 0.4"
- Product Width
- 14.0"
- Product Length
- 13.0"
What’s in the Box
- 1 x Shim Kit (0.002", 0.003", 0.005", 0.010" shims) (Replaces 15-31535A1)
Installation Notes
- Ensure the engine is off and the drive is safely secured before starting work.
- Disassemble the lower unit to access the bearing carrier, following your specific model's service manual.
- Remove the old bearing carrier and shims, cleaning all mating surfaces thoroughly.
- Select the appropriate combination of new shims from the kit to achieve the required gear backlash and bearing preload. This is a critical step that requires precise measurement with a dial indicator.
- Install the new shims and reinstall the bearing carrier.
- Torque all fasteners to the manufacturer's specified values.
- Reassemble the drive unit, refill with gear lube, and test for proper operation.
Troubleshooting & FAQ
How do I know if this shim kit will fit my specific Mercruiser model?
The best way to confirm is by checking your engine's serial number against the ranges provided in the Engine & Model Compatibility table. This kit is designed for a broad range of models from 1962–1977 and newer Alpha One Gen II counter-rotation drives.
What is the purpose of this shim kit?
This shim kit is used to set the correct distance and clearance (preload and backlash) for the gears and bearings within the sterndrive's lower unit. Proper shimming is essential for quiet operation, smooth shifting, and preventing premature gear wear.
Are all the shim thicknesses required for installation?
No. You will use a specific combination of the included shims to achieve the precise measurements required by your drive's service manual. The variety of thicknesses allows for fine-tuned adjustments.
What are signs that my old shims or bearings need replacement?
Common symptoms include a grinding or whining noise from the drive unit, excessive vibration, difficulty shifting, or the presence of metal shavings in the gear lube. These indicate internal wear that may require disassembly and re-shimming.
Is this kit for standard or counter-rotation drives?
This kit fits a wide array of standard rotation drives from 1962-1977, and it is also explicitly compatible with Mercruiser Alpha One Generation II Counter Rotation models from 1991 and newer.
Why are there different thicknesses included in the kit?
The different thicknesses (0.002", 0.003", 0.005", 0.010") allow a technician to create the exact total shim stack thickness needed to meet the manufacturer's specification for gear alignment and bearing preload, compensating for manufacturing tolerances in the housing and components.
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.
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