Mercury Gearcase Seal Kit – Fits Mercury 65-115 HP Outboards (Replaces 8M0088080)
This gearcase seal kit is designed for Mercury FourStroke and Pro XS 65-115 HP outboard engines (2004–present). It provides the essential components needed to service and reseal the lower unit, preventing water intrusion and oil leaks.
It serves as a direct replacement for Mercury OEM part number 8M0088080.
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Installation: Designed for a direct OEM replacement fit.
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Function: Restores gearcase integrity by replacing worn or damaged seals.
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Compatibility: Engineered for a wide range of Mercury 65, 75, 80, 90, 100, and 115 HP 4-Stroke models.
Part Number Cross-Reference
Use this table to confirm equivalent part numbers across OEM and aftermarket brands.
Brand |
Part Number |
Mercury |
8M0088080 |
Compatible Engine Models
Confirm your engine model/year in the table below. For Mercury owners, here’s a guide to help you identify your engine’s serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.
Brand |
Model |
Rated HP |
Stroke |
Years |
OEM Part No. |
Notes |
Mercury |
FourStroke |
65 |
4-Stroke |
2004–Present |
8M0088080 |
|
Mercury |
FourStroke |
75 |
4-Stroke |
2004–Present |
8M0088080 |
|
Mercury |
FourStroke |
80 |
4-Stroke |
2004–Present |
8M0088080 |
International model |
Mercury |
FourStroke |
90 |
4-Stroke |
2004–Present |
8M0088080 |
|
Mercury |
FourStroke |
100 |
4-Stroke |
2004–Present |
8M0088080 |
International model |
Mercury |
FourStroke |
115 |
4-Stroke |
2004–Present |
8M0088080 |
|
Mercury |
Pro XS |
115 |
4-Stroke |
2004–Present |
8M0088080 |
|
Mercury |
SeaPro |
75 |
4-Stroke |
2004–Present |
8M0088080 |
|
Mercury |
SeaPro |
90 |
4-Stroke |
2004–Present |
8M0088080 |
|
Mercury |
SeaPro |
115 |
4-Stroke |
2004–Present |
8M0088080 |
|
Mercury |
Jet |
65 |
4-Stroke |
2004–Present |
8M0088080 |
Based on 80-90HP powerhead |
Mercury |
Jet |
80 |
4-Stroke |
2004–Present |
8M0088080 |
Based on 100-115HP powerhead |
Technical Specifications
Specification |
Value |
Product Type |
Gearcase Seal Kit |
Installation |
Direct OEM replacement |
Other Technical Attributes |
Kit contains multiple seals and components for gearcase service |
Package Contents
1 x Gearcase Seal Kit (Replaces 8M0088080)
Installation Guide
- Ensure the engine is off and securely positioned. Turn off the battery switch or disconnect the battery.
- Place a drain pan under the gearcase. Remove the lower drain/fill plug and the upper vent plug to drain the gear lube completely.
- Remove the propeller, thrust washer, and any related hardware. Inspect for fishing line, which can damage seals.
- Unbolt the gearcase from the outboard's driveshaft housing and carefully lower it.
- Disassemble the gearcase as necessary to access the propeller shaft and driveshaft seals.
- Carefully pry out the old seals and O-rings using a seal puller, being cautious not to damage the housing surfaces.
- Thoroughly clean all sealing surfaces and component bores to remove any old adhesive or debris.
- Lubricate the new seals with a light coat of 2-4-C grease and press them into place using a suitable driver until they are properly seated.
- Reassemble all components in the reverse order of disassembly, ensuring correct alignment.
- Torque all bolts and nuts to the manufacturer's recommended specifications.
- Refill the gearcase with new, high-quality marine gear lubricant until it flows from the upper vent hole, then reinstall both plugs.
- After a short period, check for any signs of oil leaks around the seals.
Troubleshooting & FAQ
Q: How do I confirm this seal kit fits my Mercury outboard?
A: This kit is designed for Mercury 65-115 HP FourStroke and Pro XS models from 2004 to the present. Please check the "Compatible Engine Models" table and cross-reference your engine's model and year. Verifying that your current part number is 8M0088080 is also a reliable method.
Q: What are the signs that my gearcase seals are failing?
A: The most common sign is milky, gray, or water-contaminated gear lube when you drain it. Other indicators include visible oil leaks around the propeller shaft housing or a persistent smell of gear oil from the lower unit. Failure to address this can lead to catastrophic gear failure.
Q: Is everything I need for the job included in this kit?
A: This kit contains the primary seals, gaskets, and O-rings needed for a standard gearcase reseal. It does not include gear lubricant, sealant/adhesive, or specialized tools (like a seal puller or press) which may be required for the installation.
Q: OEM vs. Aftermarket?
A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.
Q: How fast do you ship and how much does it cost?
A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.
Q: What is your warranty and return policy?
A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.
Important Notes
- Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
- This product is an aftermarket replacement part and is not an OEM component.
- Professional installation is recommended to ensure safety and optimal performance.
Why Choose JLM MARINE?
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Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
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Fast Global Shipping: Free delivery worldwide in 5–15 days.
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Direct from Manufacturer: Competitive pricing without compromising quality.