Lower Unit Gearcase Seal Kit for Select Mercury/Mariner Outboards – Replaces OEM 26-43035A4
Lower Unit Gearcase Seal Kit for Select Mercury/Mariner Outboards – Replaces OEM 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 Select Mercury/Mariner Outboards –...
Lower Unit Gearcase Seal Kit for Select Mercury/Mariner Outboards – Replaces OEM 26-43035A4 is backordered and will ship as soon as it is back in stock.
Product Details
This Lower Unit Gearcase Seal Kit is an aftermarket replacement for servicing the gear housing and lower unit on select Mercury and Mariner outboards. The applicable manufacturer reference is 26-43035A4. Catalog records identify this seal kit in Mercury gear-housing diagrams, including selected 30, 40, 45, 50, 55, and 60 HP applications with model, gear-ratio, and serial-number conditions.
Fitment is determined by the gearcase design and the engine's exact model and serial number, not horsepower alone. Confirm the complete application information before ordering, especially where the catalog specifies a 2.31:1 or 2.33:1 gear ratio, Bigfoot configuration, or a defined serial-number range.
- Designed for lower-unit and gear-housing seal service.
- Replaces the Mercury/OEM reference 26-43035A4.
- Includes oil seals, gaskets, washers, and an O-ring for the listed seal-kit application.
- Aftermarket replacement part; not manufactured by Mercury or Mariner.
Part Number References
Use the following references to compare the replacement part with your original component. Cross-reference numbers do not replace model and serial-number verification.
| Reference Type | Part Number | Application |
|---|---|---|
| OEM / manufacturer reference | 26-43035A4 | Mercury/Mariner lower unit gear-housing seal kit reference |
| Aftermarket reference | 18-2624 | Sierra lower unit seal kit reference listed as replacing 26-43035A4 |
Engine & Model Compatibility
The verified catalog occurrences below show the reference in specific Mercury gear-housing diagrams. These entries preserve the serial-number and configuration conditions supplied by the catalog. They are examples of documented applications, not a claim that every engine in the same horsepower class fits.
| Brand | Model / Configuration | Rated HP | Stroke | Serial / Application Condition | Gear-Housing Reference |
|---|---|---|---|---|---|
| Mercury | 30 JET, 3-cylinder | 30 | Not specified | 0G760300 through 0T408999 | Propeller shaft, 2.31:1 |
| Mercury | 30 JET, 3-cylinder | 30 | Not specified | 0P017000 through 0P153499 | Propeller shaft, 2.31:1 |
| Mercury | 40, 4-stroke | 40 | 4-Stroke | 0G231123 through 0G760299 | Propeller shaft, 2.31:1 |
| Mercury | 40, 4-stroke | 40 | 4-Stroke | 0G760300 through 0T408999 | Propeller shaft, 2.31:1 |
| Mercury | 40, 4-stroke | 40 | 4-Stroke | 9944807 through 0P016999 | Propeller shaft, 2.31:1 |
| Mercury | 40, 4-stroke, 4-cylinder | 40 | 4-Stroke | 0T178500 through 0T598999 | Propeller shaft, 2.31:1 |
| Mercury | 40, 4-stroke, 4-cylinder | 40 | 4-Stroke | 0P094500 through 0P206999 | Propeller shaft, 2.31:1 |
| Mercury | 40 JET | 40 | Not specified | 0T178500 through 0T979999 | 2.31:1 or 2.33:1 propeller-shaft gear housing |
| Mercury | 40 JET | 40 | Not specified | 0T980000 and up | Propeller shaft, 2.33:1 |
| Mercury | 45 JET | 45 | Not specified | 9973100 through 0P016999 | Drive-shaft and propeller-shaft diagrams, 2.31:1 |
| Mercury | 45 Bodensee | 45 | 4-Stroke | 0P017000 through 0P094499 | 2.31:1 or 2.33:1 propeller-shaft gear housing |
| Mercury | 50 Bigfoot | 50 | 4-Stroke | 0G231123 through 0G760299; 0G760300 through 0T178499; 9944807 through 0P016999; 0P017000 through 0P094499 | Bigfoot propeller-shaft gear housing, 2.31:1 |
| Mercury | 50, 4-cylinder | 50 | 4-Stroke | 0T178500 through 0T598999 or 0P094500 through 0P206999 | Propeller shaft, 2.31:1 |
| Mercury | 55, 3-cylinder | 55 | Not specified | 0D000750 through 0G290584; 0G290585 through 0G589999; 0G590000 through 0G760299 | Bigfoot, SeaPro/Marathon, drive-shaft, or propeller-shaft diagrams as applicable |
| Mercury | 60, 3-cylinder | 60 | Not specified | 0D000750 through 0G290584; 0G290585 through 0G589999; 0G590000 through 0G760299; 0G760300 through 0T979999; 0T980000 and up | Bigfoot or propeller-shaft gear housing, 2.31:1 or 2.33:1 as applicable |
| Mercury | 60, 4-cylinder | 60 | 4-Stroke | 0T178500 through 0T598999 or 0P094500 through 0P206999 | Propeller shaft, 2.31:1 |
Some aftermarket catalogs list the 26-43035A4 reference across a broader 30–125 HP range. Because the available catalog records show different model, gear-ratio, and serial-number conditions, do not use the horsepower range by itself to confirm fitment.
Technical Specs
- Product Type
- Lower Unit Gearcase Seal Kit
- Replacement Reference
- OEM 26-43035A4
- Aftermarket Reference
- Sierra 18-2624
- Application
- Selected Mercury and Mariner gear housings; verify model, serial number, and gearcase configuration
- Installation
- Replacement service part; professional installation is recommended
- Fuel Type
- Not applicable
What’s in the Box
The documented 18-2624 replacement configuration contains the following service parts. Quantities are shown where the catalog provides them:
| Quantity | Component | Aftermarket Component Reference | Corresponding OEM Reference |
|---|---|---|---|
| 1 | Oil seal | 18-0522 | 26-43036 |
| 1 | Oil seal | 18-0583 | 26-43035 |
| 1 | Oil seal | 18-2002 | 26-30550, 26-76868 |
| 1 | Oil seal | 18-2053 | 26-70081 |
| 1 | Oil seal | 18-2054 | 26-8164641 |
| 1 | Face-plate-to-water-pump-cover gasket | 18-2563 | 27-43034-1 |
| 1 | Water-pump-base-to-face-plate gasket | 18-2564 | 27-43033-1 |
| 1 | Water-pump-base-to-gear-housing gasket | 18-2565 | 27-43047-2 |
| 1 | Face-plate-to-water-pump-cover gasket | 18-2566 | 27-817277 |
| 3 | Washer | 18-2945 | 12-19183 |
| 1 | Washer | 18-4261 | 19643 |
| 1 | O-ring | 18-7198 | 25-45710 |
Do not assume that bearings, gears, a water-pump impeller, lubricant, sealant, or other internal hard parts are included unless they are listed above.
Installation Notes
- Confirm the engine model, serial number, gearcase configuration, and original seal-kit dimensions before disassembly.
- Disconnect the battery and safely drain the gearcase lubricant into an approved container.
- Remove the lower unit according to the engine manufacturer's service procedure and retain all hardware.
- Disassemble only as required for the seals and gaskets being replaced. Record the orientation of seals, shafts, washers, and gaskets.
- Remove old seals and gaskets without damaging the housing, shaft surfaces, or mating faces.
- Clean and inspect all mating surfaces. Replace damaged shafts, bearing carriers, or housings before installing new seals.
- Install the replacement components in their correct locations and orientations. Use suitable marine lubricant or sealant only where specified by the service procedure.
- Reassemble and torque fasteners according to the engine manufacturer's specifications.
- Refill the gearcase with the correct lubricant and check for leaks after installation.
- After operation, inspect the lubricant for water contamination or a milky appearance and recheck for external leakage.
Troubleshooting & FAQ
How do I confirm fitment?
Compare the complete engine model and serial number, gearcase type, gear ratio, original seal arrangement, and OEM reference with the application information above. Horsepower alone is not sufficient.
Does this kit replace OEM 26-43035A4?
Yes. The documented aftermarket reference 18-2624 is listed as replacing OEM 26-43035A4. The replacement part remains subject to the original engine and gearcase application conditions.
What symptoms can indicate a lower-unit seal problem?
Possible symptoms include water-contaminated or milky gear oil, lubricant around the propeller-shaft or driveshaft area, or visible leakage from the gear housing. Inspect the complete lower unit before ordering replacement parts.
Does the kit rebuild the entire gearcase?
No. It is a seal-and-gasket service kit. It does not include bearings, gears, shafts, a complete gearcase, or other internal hard parts.
Is this an OEM Mercury part?
No. This is an aftermarket replacement kit cross-referenced to OEM 26-43035A4. Mercury and Mariner are mentioned only to describe the documented application and reference numbers.
Safety & Important Information
- Verify the exact model, serial number, gear ratio, and original part before purchase.
- Do not install a seal or gasket that is damaged, contaminated, or visibly different from the original component.
- Follow the engine manufacturer's service procedures and torque specifications.
- Professional installation is recommended for lower-unit disassembly and reassembly.
About Sea Sierra
- Marine Replacement Parts — Replacement components for common outboard service applications.
- Application-Focused Information — Product references are provided to help match the part to the correct engine and gearcase.
- Aftermarket Value — Practical replacement options for maintenance and repair projects.
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