Lower Unit Gearcase Seal Kit for Mercury, Mariner and Force Outboards, 30–125 HP – Replaces Mercury 26-43035A4
Lower Unit Gearcase Seal Kit for Mercury, Mariner and Force Outboards, 30–125 HP – Replaces Mercury 26-43035A4 is backordered and will ship as soon as it is back in stock.
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Lower Unit Gearcase Seal Kit for Mercury, Mariner and Force Outboar...
Lower Unit Gearcase Seal Kit for Mercury, Mariner and Force Outboards, 30–125 HP – Replaces Mercury 26-43035A4 is backordered and will ship as soon as it is back in stock.
Product Details
This lower unit gearcase seal kit is intended as an aftermarket replacement for selected Mercury, Mariner and Force outboard gearcases in the 30–125 HP range. The listed applications include both 2-stroke and 4-stroke engines and lower units using either a 3-jaw or 6-jaw reverse clutch. Always compare the engine model, horsepower, year and serial-number range before ordering.
The kit is listed as an interchange for Mercury part numbers 26-43035A4, 26-43035A3, 26-43035A2 and 26-43035A1. Additional aftermarket reference numbers include Sierra 18-2626, GLM 87590 and Mallory 9-74200.
- Aftermarket replacement for servicing the lower-unit gearcase sealing system.
- Applications include selected 3-jaw and 6-jaw reverse-clutch lower units.
- Includes seals, gaskets and O-rings specified for the listed applications.
- Installation requires gearcase disassembly and should follow the applicable service manual.
Part Number Matrix
Use these references to compare the listed OEM and aftermarket numbers with the part being replaced.
| Brand | Part Number |
|---|---|
| Mercury | 26-43035A4 |
| Mercury | 26-43035A3 |
| Mercury | 26-43035A2 |
| Mercury | 26-43035A1 |
| Sierra | 18-2626 |
| GLM | 87590 |
| Mallory | 9-74200 |
Engine & Model Compatibility
The following applications are the listed fitment references for this seal kit. Model, year, stroke type and serial-number conditions should be considered together; a horsepower match alone does not confirm compatibility.
| Brand | Model or Configuration | Rated HP | Stroke | Years | Reference Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury/Mariner | 2-Stroke | 100/115/125 | 2-Stroke | 1991 and newer | 26-43035A4 | USA 0B209468 and newer; Belgium 9523034 and newer; 3- or 6-jaw reverse clutch. |
| Mercury/Mariner | 4-Stroke BIGFOOT | 50 | 4-Stroke | 1991–2010 | 26-43035A4 | Verify the exact model and serial number. |
| Mercury/Mariner | 3-cylinder BIGFOOT | 60 | 4-Stroke | 1991–2010 | 26-43035A4 | Verify the exact model and serial number. |
| Mercury/Mariner | 3-cylinder | 70 | 4-Stroke | 1991–2010 | 26-43035A4 | USA 0A996142 and newer; Belgium 9483121 and newer. |
| Mercury/Mariner | 3-cylinder | 75 | 4-Stroke | 1991–2010 | 26-43035A4 | USA 0C222000 and newer; Belgium 9589039 and newer. |
| Mercury/Mariner | 3-cylinder | 80/90 | 4-Stroke | 1991–2010 | 26-43035A4 | Verify the exact model and serial number. |
| Mercury/Mariner | 4-cylinder | 100/115/125 | 4-Stroke | 1991–2010 | 26-43035A4 | Verify the exact model and serial number. |
| Mercury/Mariner | 3-cylinder | 30–90 | 2-Stroke | 1991–2010 | 26-43035A4 | Verify the exact model and serial number. |
| Mercury/Mariner | 4-cylinder | 45–90 | 2-Stroke | 1991–2010 | 26-43035A4 | Verify the exact model and serial number. |
| Mercury | Outboard | 30 | 2-Stroke | 1999–2001 | 26-43035A4 | Verify the exact model and serial number. |
| Mercury | Outboard | 40 | 2-Stroke | 1995–2007 | 26-43035A4 | Verify the exact model and serial number. |
| Mercury | Outboard | 45 | 2-Stroke | 1991–2004 | 26-43035A4 | Verify the exact model and serial number. |
| Mercury | Outboard | 50 | 2-Stroke | 1991–2007 | 26-43035A4 | Excludes 2003–2005 applications. |
| Mercury | Outboard | 55 | 2-Stroke | 1991–2006 | 26-43035A4 | Verify the exact model and serial number. |
| Mercury | Outboard | 60 | 2-Stroke | 1991–2007 | 26-43035A4 | Verify the exact model and serial number. |
| Mercury | Outboard | 65 | 2-Stroke | 1994–1998 | 26-43035A4 | Verify the exact model and serial number. |
| Mercury | Outboard | 70 | 2-Stroke | 1983, 1987–1990 | 26-43035A4 | Verify the exact model and serial number. |
| Mercury | Outboard | 75 | 2-Stroke | 1987 and newer | 26-43035A4 | Verify the exact model and serial number. |
| Mercury | Outboard | 80 | 2-Stroke | 1987–1990, 2005 and newer | 26-43035A4 | Verify the exact model and serial number. |
| Mercury | Outboard | 90 | 2-Stroke | 1987 and newer | 26-43035A4 | Verify the exact model and serial number. |
| Mercury | Outboard | 100 | 2-Stroke | 2001–2007 | 26-43035A4 | Verify the exact model and serial number. |
| Mercury | Outboard | 115 | 2-Stroke | 1994–1996, 2001 and newer | 26-43035A4 | Verify the exact model and serial number. |
| Mercury | Outboard | 125 | 2-Stroke | 1997–2000, 2004 and newer | 26-43035A4 | Verify the exact model and serial number. |
| Force | Outboard | 75 | 2-Stroke | 1999 | 26-43035A4 | Verify the exact model and serial number. |
| Force | Outboard | 90 | 2-Stroke | 1995–1999 | 26-43035A4 | Verify the exact model and serial number. |
| Force | Outboard | 120 | 2-Stroke | 1995–1999 | 26-43035A4 | Verify the exact model and serial number. |
Technical Specs
- Product Type
- Lower unit and gearcase seal kit
- Application
- Selected Mercury, Mariner and Force outboard gearcases
- Rated Horsepower Range
- 30–125 HP, subject to the listed model, year and serial-number conditions
- Stroke Coverage
- Selected 2-stroke and 4-stroke applications
- Reverse Clutch Compatibility
- Selected 3-jaw and 6-jaw reverse-clutch lower units
- Installation
- Replacement installation; follow the applicable service manual
What's in the Box
- Various oil seals
- Various gaskets
- Various O-rings
- Drain-screw gasket(s)
- Water-line seal(s)
- Impeller gasket(s)
- Washer(s)
- Insulator bushing(s)
- Drive-shaft oil seal(s)
Exact component styles and quantities may vary by application within the listed fitment range. Compare the kit contents with the original gearcase components before installation.
Installation Notes
- Secure the outboard on a suitable stand or position it so the lower unit can be accessed safely.
- Place a drain pan under the gearcase and remove the gear-lube drain and vent screws. Allow the lubricant to drain completely.
- Remove the fasteners securing the lower unit and carefully separate the lower unit from the engine housing.
- Use the applicable service manual to disassemble the gearcase and access the seals, gaskets and O-rings.
- Remove the old sealing components and clean the sealing surfaces, checking for debris, corrosion or damage.
- Install the replacement components from the kit using the correct orientation and installation tools. Lubricate components only as specified by the service manual.
- Reassemble the gearcase and torque fasteners to the manufacturer's specifications.
- Reinstall the lower unit onto the engine.
- Fill the gearcase with the specified marine gear lubricant through the lower drain opening until lubricant appears at the upper vent opening.
- Install the vent and drain screws with the appropriate new gaskets, then check for leaks after service.
Troubleshooting & FAQ
How do I confirm fitment for my engine?
Compare the engine brand, model or configuration, horsepower, stroke type, year and serial number with the compatibility table. Confirm the existing reference number and reverse-clutch design where applicable. If any of these conditions differ, consult the applicable parts diagram or service information before ordering.
What are common signs of failing gearcase seals?
Milky or light-colored gear lubricant can indicate water intrusion. Oil around the propeller-shaft area or drain and vent screws may indicate leakage. A gearcase that has been operated with contaminated or insufficient lubricant may also develop abnormal noise or wear.
Does the kit fit both 3-jaw and 6-jaw reverse clutches?
The listed applications include lower units with either 3-jaw or 6-jaw reverse-clutch designs. Confirm the engine and lower-unit conditions in the compatibility information before installation.
When should lower-unit seals be inspected?
Inspect gear lubricant during routine maintenance and whenever the gearcase is serviced. Replace damaged or leaking seals and use new sealing washers or gaskets where specified by the service manual.
Is this an OEM part?
No. This is an aftermarket replacement kit listed for interchange with the reference numbers shown on this page.
Safety & Important Information
- Verify the engine model, year, horsepower, stroke type, serial-number range and lower-unit configuration before purchase.
- Reference numbers are supplied for comparison and do not replace application verification.
- Do not install components that differ in size, style or configuration from the applicable service information.
- Gearcase disassembly and seal replacement should be performed by a qualified technician using the correct service manual and torque specifications.
- This is an aftermarket replacement, not an OEM component.
About Sea Sierra
- Marine Replacement Parts — Replacement components for selected marine service applications.
- Application-Focused Information — Model, year, horsepower and serial-number conditions are provided to support fitment checks.
- Aftermarket Value — A replacement option for servicing compatible marine equipment.
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