Gearcase Seal Kit – Fits Mercury 65HP 75HP 80HP 90HP 100HP 115HP (Replaces 8M0088080)

Product Details

This Gearcase Seal Kit – Fits Mercury 65HP 75HP 80HP 90HP 100HP 115HP (Replaces 8M0088080) is designed for Mercury outboard engines from 65HP to 115HP EFI models, including standard, Sea Pro, Pro XS, and JET variants with serial numbers 2B095049 & Up (2B225488 & Up for 115HP Pro XS). The kit services both gear housing driveshaft and propeller shaft assemblies with 2.07:1 standard rotation gearcase configurations.

This aftermarket seal kit directly replaces Mercury OEM part number 8M0088080, providing an exact-fit alternative for lower unit maintenance and repair.

• Compatible with EFI, Sea Pro, Pro XS, and JET engine variants
• Services both driveshaft and propeller shaft gear housing assemblies
• Engineered for 2.07:1 standard rotation gearcases

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Engine & Model Compatibility

Confirm your engine model/year in the table below.

Technical Specs

OEM Part Number

8M0088080

Application

Gearcase seal kit for gear housing driveshaft and propeller shaft assemblies

Gear Ratio

2.07:1 Standard Rotation

Compatibility

Mercury 65HP, 75HP, 80HP, 90HP, 100HP, 115HP EFI outboards

What's in the Box

• Gearcase Seal Kit (complete set)

Installation Notes

1. Disconnect battery and remove propeller before beginning service.
2. Drain gear oil completely and inspect for metal shavings or contamination.
3. Remove lower unit from engine following manufacturer's service manual procedures.
4. Disassemble gearcase housing and remove old seals from driveshaft and propeller shaft assemblies.
5. Clean all seal mating surfaces thoroughly, removing residue and corrosion.
6. Lubricate new seals with marine-grade gear oil before installation.
7. Install new seals carefully, ensuring proper orientation and seating without damage.
8. Reassemble gearcase components per torque specifications in service manual.
9. Reattach lower unit to engine, verifying all fasteners and shift linkages are secure.
10. Refill gearcase with recommended gear oil to proper level through fill plug.
11. Reinstall propeller and test shift operation before launching.
12. Monitor for leaks during initial operation and re-check oil level after first use.

Troubleshooting & FAQ

How do I know if my gearcase seals need replacement?

Common signs include gear oil leaking from the lower unit, milky or contaminated gear oil indicating water intrusion, or visible oil around the propeller shaft. Regular inspection during seasonal maintenance is recommended.

Will this kit work on both driveshaft and propeller shaft assemblies?

Yes, this seal kit is designed to service both the gear housing driveshaft and propeller shaft components on compatible Mercury outboard models with 2.07:1 standard rotation gearcases.

What tools are required for installation?

Basic lower unit removal tools, seal installation drivers or appropriate sockets, torque wrench, gear oil pump, and your engine's service manual. Special seal drivers help prevent damage during installation.

How often should gearcase seals be replaced?

Replace seals whenever the lower unit is disassembled for service, if leaks are detected, or as preventive maintenance every 3–5 years depending on usage and operating conditions. Saltwater environments may require more frequent inspection.

Can I use this on a counter-rotation gearcase?

This kit is specified for 2.07:1 standard rotation gearcases. Verify your gearcase rotation type and ratio before ordering to ensure proper fitment.

What type of gear oil should I use after seal replacement?

Use Mercury Premium or High-Performance Gear Lube as specified in your owner's manual. Proper oil viscosity and type are critical for seal longevity and gearcase protection.

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 against 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.