Gearcase Seal Kit – Fits Mercury/Mariner 75-100HP Outboards (Replaces 26-43035A4)
Gearcase Seal Kit – Fits Mercury/Mariner 75-100HP Outboards (Replaces 26-43035A4) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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
Gearcase Seal Kit – Fits Mercury/Mariner 75-100HP Outboards (Replac...
Product Details
This aftermarket Gearcase Seal Kit – Fits Mercury/Mariner 75-100HP Outboards (Replaces 26-43035A4) is designed for Mercury and Mariner 75-100HP 4-Stroke outboard engines manufactured from 1998 to the present. It provides the necessary components to restore sealing integrity in the lower unit, preventing water intrusion and lubricant leaks.
This kit serves as a direct replacement for Mercury OEM part 26-43035A4, as well as Sierra 18-2626 and GLM 87590 aftermarket equivalents.
- Professional installation is recommended for proper fit and function.
- The kit includes a comprehensive set of seals, applicators, and related hardware for a complete service.
- Engineered to meet or exceed original factory specifications for reliable performance.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 26-43035A4 |
| Sierra | 18-2626 |
| GLM | 87590 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This kit is verified for compatibility with the following Mercury and Mariner outboard models.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury/Mariner | 75HP | 75 | 4-Stroke | 1998–present | 26-43035A4 | Also fits Force outboards |
| Mercury/Mariner | 80HP | 80 | 4-Stroke | 1998–present | 26-43035A4 | Also fits Force outboards |
| Mercury/Mariner | 90HP | 90 | 4-Stroke | 1998–present | 26-43035A4 | Also fits Force outboards |
| Mercury/Mariner | 100HP | 100 | 4-Stroke | 1998–present | 26-43035A4 | Also fits Force outboards |
Technical Specs
- Product Type
- Lower Unit Gearcase Seal Kit
- Housing Material
- Various (rubber, metal, composite)
- Dimensions
- 28.0 × 18.0 × 3.0 inches (711.2 × 457.2 × 76.2 mm)
- Weight
- 4.54 kg (10 lb)
- Warranty
- 1 Year
- Shelf Life
- 9 Months
What’s in the Box
- 1 x Gearcase Seal Kit (26-43035A4) containing:
- 1 x Blade High Carbon Razor 100/Pack
- 1 x Nozzle #8630
- 1 x Celcon Scraper
- 1 x A21 Scotch-Brite Sponge
- 1 x Bottle Poly 6 oz with Pump Sprayer
- 1 Pair x Nitrile Gloves Purple Small
- 1 Pair x Nitrile Gloves Purple Medium
- 1 Pair x Nitrile Gloves Purple Large
- 1 x Guide Strip (HSKSTRIP) 1/16"T × 1/4"W × 18"L
- 1 x Masking Tape PG-5 Inter-Tape 1" × 60 YD
- 1 x UNI-CER 90 ST 2 oz Jar
- 1 x Kimberly Clark 34155 4.4" × 8.4" 1-Ply 286/Box
- 1 x 1425CF/2IK654SKN (PR-1425CF B 1/2 654SK)
- 1 x 1861XXXXCA004DAHSK (PR1861 ADH Pro 4D BTL)
- 1 x 226865 Ram Rod 8" Black
- 1 x Hump Seal Shaping Tool (A3T22082156/A3T22082219/A3T22082155 depending on model)
Installation Notes
Professional installation is strongly recommended. The general process involves draining the gear lube, removing the lower unit, disassembling the carrier and prop shaft assemblies to access the old seals, thoroughly cleaning all surfaces of old sealant and debris, and carefully installing the new seals and O-rings using appropriate drivers and sealant as specified by the manufacturer's service manual.
Troubleshooting & FAQ
How do I know if this seal kit fits my engine?
Confirm your exact engine model, horsepower, and year fall within the ranges specified in the "Engine & Model Compatibility" table. Cross-reference your existing part number with those in the "Part Number Matrix" to ensure it's a correct replacement for 26-43035A4, Sierra 18-2626, or GLM 87590.
What are the signs of a failing gearcase seal?
Common symptoms include milky or gray-colored gear lube (indicating water intrusion), visible oil leaking from the propeller shaft or driveshaft area, or a persistent smell of gear oil around the lower unit. You may also notice fishing line tangled around the prop shaft, which can damage seals over time.
Is professional installation necessary?
While some experienced home mechanics may perform the replacement, professional installation is highly recommended. The process requires specialized tools, such as a seal puller and driver set, and knowledge of correct seal orientation and depth to prevent premature failure.
How often should gearcase seals be replaced?
Seals should be inspected during every routine lower unit service (typically annually or every 100 hours) and replaced immediately if there are any signs of leaks or damage. It is also good practice to replace them proactively every 3-5 years, depending on usage and operating conditions.
What's the difference between this aftermarket kit and the OEM version?
Our aftermarket kit is engineered to provide the same form, fit, and function as the original OEM part. It is made with comparable materials and manufactured in a facility that adheres to strict quality control standards to ensure reliable, long-lasting performance at a better value.
Does this kit include everything I need for the replacement?
This kit includes a comprehensive set of seals, O-rings, and other components required for the job as detailed in the "What's in the Box" section. However, you will still need tools, gear lube, and potentially chemical cleaners or thread lockers, which are not included.
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.
Payment & Security
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