Lower Unit Gearcase Seal for Mercury/Mariner 135 HP and 150 HP FourStroke Outboards – OEM References 8M0057716 and 46-8M0057716
Lower Unit Gearcase Seal for Mercury/Mariner 135 HP and 150 HP FourStroke Outboards – OEM References 8M0057716 and 46-8M0057716 is backordered and will ship as soon as it is back in stock.
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Lower Unit Gearcase Seal for Mercury/Mariner 135 HP and 150 HP Four...
Lower Unit Gearcase Seal for Mercury/Mariner 135 HP and 150 HP FourStroke Outboards – OEM References 8M0057716 and 46-8M0057716 is backordered and will ship as soon as it is back in stock.
Product Details
This lower unit gearcase seal is designed for service of selected Mercury and Mariner FourStroke outboard gearcases. It is listed for Mercury 135 HP EFI FourStroke, Mercury 150 HP EFI FourStroke, and Mercury 150 HP SeaPro commercial FourStroke applications within the serial-number ranges shown below.
The product is associated with Mercury OEM references 8M0057716 and 46-8M0057716. Verify the complete engine model and serial number before ordering or installing.
- Intended for lower unit and gearcase sealing service.
- Helps restore the sealing function at the applicable gearcase service location.
- Fitment depends on the exact engine model and serial-number range; horsepower alone is not sufficient for confirmation.
Part Number Matrix
Use these manufacturer references when comparing the original component with this replacement.
| Brand | Manufacturer Reference |
|---|---|
| Mercury | 8M0057716 |
| Mercury | 46-8M0057716 |
Engine & Model Compatibility
The following applications are listed for this product. Keep the model, horsepower, stroke, brand, and serial-number conditions together when confirming fitment.
| Brand | Model/Application | Rated HP | Stroke | Serial Number | Manufacturer Reference |
|---|---|---|---|---|---|
| Mercury | EFI | 135 | 4-Stroke | 2B131942 and up | 8M0057716; 46-8M0057716 |
| Mercury/Mariner | EFI | 150 | 4-Stroke | 1B905505 and up | 8M0057716; 46-8M0057716 |
| Mercury | SeaPro, commercial | 150 | 4-Stroke | 2B139139 and up | 8M0057716; 46-8M0057716 |
Technical Specifications
- Product Type
- Lower unit gearcase seal component
- Service Area
- Outboard gearcase/lower unit
- Applicable Engine Type
- Selected Mercury and Mariner 4-Stroke outboards
- Manufacturer References
- 8M0057716 and 46-8M0057716
Package Contents
This listing is for the gearcase seal component identified above. The company product record does not specify a component quantity, additional gaskets, O-rings, installation hardware, or a complete rebuild-kit package. Do not assume that bearings, gears, fasteners, lubricant, or other service parts are included.
Installation Notes
- Confirm the engine brand, model/application, stroke, and serial number against the compatibility table before beginning service.
- Secure the outboard according to the manufacturer's service procedures and place a suitable drain pan beneath the lower unit if gear lubricant will be drained.
- Remove the related gearcase components required to access the sealing location. Record the position and orientation of all parts during disassembly.
- Remove the old seal carefully and clean the mating and sealing surfaces without damaging the housing, shaft, or bore.
- Install the replacement seal using the correct tools and procedure for the specific engine and sealing location. Use only lubricants and sealants approved by the engine manufacturer.
- Reassemble the gearcase with the correct torque values and replacement fasteners where required by the service manual.
- Refill the gearcase with the manufacturer-recommended lubricant if the service procedure requires draining it, then inspect for leaks before returning the engine to service.
Gearcase disassembly and seal replacement can require specialized tools and a pressure or vacuum leak test. Professional installation is recommended when the applicable service procedure is not available.
Troubleshooting & FAQ
How can I identify a failing gearcase seal?
Possible signs include milky or creamy gear lubricant, lubricant visible around the propeller shaft or gearcase, or failure during a pressure or vacuum test. Inspect the full gearcase and confirm the actual leak location before replacing a seal.
Will this seal fit any Mercury or Mariner 135 HP or 150 HP outboard?
No. The listed fitment is limited to the applications and serial-number ranges in the compatibility table: Mercury 135 HP EFI FourStroke from serial number 2B131942 and up, Mercury/Mariner 150 HP EFI FourStroke from serial number 1B905505 and up, and Mercury 150 HP SeaPro commercial FourStroke from serial number 2B139139 and up.
Is this a complete gearcase rebuild kit?
No complete rebuild-kit contents are specified for this product record. Bearings, gears, gaskets, O-rings, hardware, lubricant, and other components should not be assumed to be included.
What should I verify before ordering?
Compare the original component and its manufacturer reference, then verify the engine brand, exact model/application, 4-Stroke configuration, horsepower, and serial number. If any of these details differ, consult the applicable service catalog or a qualified marine technician.
What maintenance is recommended?
Inspect gear lubricant during the manufacturer's recommended service interval and after any lower-unit impact or disassembly. Replace the seal if leakage is confirmed or if the service procedure requires replacement during disassembly.
Shipping speed and cost?
Shipping availability, delivery time, and cost are shown at checkout and may vary by destination and service level.
Warranty and returns?
Warranty coverage and return eligibility are governed by the current store policies. Contact support before returning a part and provide the order details and fitment information.
Safety & Important Information
- Verify the engine serial number and application before purchase; horsepower alone does not confirm compatibility.
- Follow the applicable Mercury or Mariner service manual for disassembly, seal installation, torque values, lubricant, and leak testing.
- Do not reuse damaged sealing surfaces or continue operating an outboard with contaminated gear lubricant or an active leak.
- Professional installation is recommended for gearcase disassembly and reassembly.
About Sea Sierra
- Marine-Focused Selection — Parts are organized by application and manufacturer reference to support accurate service-part matching.
- Fitment-Conscious Support — Confirm the complete model and serial-number conditions before ordering.
- Service-Ready Information — Product pages identify the intended service area and important installation considerations.
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