Lower Unit Assembly – Fits Mercury/Mercruiser 40-60 HP EFI 4-Stroke (Replaces 1667-9011J41)
Lower Unit Assembly – Fits Mercury/Mercruiser 40-60 HP EFI 4-Stroke (Replaces 1667-9011J41) is backordered and will ship as soon as it is back in stock.
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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).
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Lower Unit Assembly – Fits Mercury/Mercruiser 40-60 HP EFI 4-Stroke...
Product Details
This is a complete Lower Unit Assembly for Mercury/Mercruiser 40-60 HP EFI 4-Stroke outboards, specifically designed for models with a 25" extra-long shaft and a 2.33:1 gear ratio. It is engineered for a precise fit on engines manufactured from approximately 2005 and later, providing a reliable, direct-fit replacement for your original gearcase.
It serves as a direct interchange for Mercury part number 1667-9011J41 and SEI Engineering REC1667-9011J41.
- Simple bolt-on installation requires no special modifications.
- Comes complete with a new water pump pre-installed.
- Built to withstand demanding marine environments.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 1667-9011J41 |
| SEI Engineering | REC1667-9011J41 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This unit is designed for specific Mercury & Mercruiser EFI 4-Stroke models requiring a 25-inch shaft.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 40 EFI | 40 | 4-Stroke | 0P153500–0P400999 | 1667-9011J41 | 25" Shaft |
| Mercury | 40 EFI | 40 | 4-Stroke | 0T409000–1B344306 | 1667-9011J41 | 25" Shaft |
| Mercury | 50 EFI | 50 | 4-Stroke | 0P153500–0P400999 | 1667-9011J41 | 25" Shaft |
| Mercury | 50 EFI | 50 | 4-Stroke | 0T409000–1B344306 | 1667-9011J41 | 25" Shaft |
| Mercury | 60 EFI | 60 | 4-Stroke | 0P153500–0P400999 | 1667-9011J41 | 25" Shaft |
| Mercury | 60 EFI | 60 | 4-Stroke | 0T409000–1B344306 | 1667-9011J41 | 25" Shaft |
Technical Specs
- Product Type
- Complete Lower Unit Assembly
- Installation
- Bolt-on replacement
- Gear Ratio
- 2.33:1
- Torpedo Diameter
- 107.95 mm (4.25 inches)
- Shaft Length
- 25" (Extra Long/XL)
- Dimensions
- Height: 129.0 cm, Width: 27.0 cm, Length: 68.5 cm
- Weight
- 24.0 kg (52.9 lbs)
- Water Pump
- Included
What’s in the Box
- 1 x Complete Gear Housing Assembly (1667-9011J41)
Installation Notes
- Disconnect the battery leads for safety.
- Place a drain pan under the gearcase and remove the drain/fill screws to empty the gear lube.
- Remove the mounting bolts securing the lower unit to the outboard midsection.
- Carefully separate the lower unit, ensuring the shift shaft linkage is disconnected.
- Clean the mounting surfaces on the midsection and inspect the driveshaft splines for wear.
- Apply marine grease to the new driveshaft splines and position the new lower unit for installation.
- Align the driveshaft, water tube, and shift shaft. Re-install the mounting bolts and torque to manufacturer specifications.
- Fill the gearcase with new, recommended marine gear lubricant until it flows from the upper vent hole.
- Install and tighten the vent and fill screws with new gaskets.
- Reconnect the battery and test the engine's shifting and operation in a safe water environment. Check for leaks.
Troubleshooting & FAQ
How do I confirm this lower unit fits my engine?
Check your engine's serial number against the ranges in the "Engine & Model Compatibility" table. You must also confirm your outboard requires a 25" (Extra Long) shaft and has a 2.33:1 gear ratio. The original OEM part number should be 1667-9011J41.
What are the signs my existing lower unit is failing?
Common symptoms include a grinding or clunking noise during shifting or operation, metal shavings in the gear lube (a small amount is normal, but large flakes are a bad sign), water in the gear lube (appearing milky or cloudy), or a bent/damaged propeller shaft.
Is the water pump and impeller included?
Yes, this is a complete assembly that includes a new, pre-installed water pump and impeller. No need to purchase these separately.
What kind of gear lube should I use?
Always use a high-quality marine gear lubricant recommended for your Mercury outboard. Check your engine's service manual for the specific weight and type (e.g., 80W-90 High Performance Gear Lube).
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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