Gearcase Seal Kit – Fits Mercury 65HP 75HP 80HP 90HP 100HP 115HP EFI (Replaces 8M0088081)

Product Details

This Gearcase Seal Kit is designed for Mercury EFI outboards including 65HP, 75HP, 80HP, 90HP, 100HP, and 115HP models with serial numbers 2B095049 and up. It covers standard and counter-rotation configurations across Sea Pro, Pro XS, and JET variants, serving both driveshaft and propeller shaft gear housing assemblies with 2.38:1 ratio.

This aftermarket kit directly replaces Mercury OEM part number 8M0088081, delivering the same fit and function at a competitive price.

• Compatible with both standard and counter-rotation gear housings
• Fits driveshaft and propeller shaft assemblies
• Designed for EFI outboard applications

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

8M0088081

Application

Gearcase assembly (driveshaft and propeller shaft)

Gear Ratio

2.38:1

Rotation Type

Standard and Counter-Rotation

Compatibility

Mercury EFI outboards 65–115 HP

Serial Number Range

2B095049 & Up (most models); 2B225488 & Up (Pro XS)

What's in the Box

• Complete gearcase seal kit with all required seals and gaskets

Installation Notes

1. Disconnect the battery and relieve all fuel pressure before beginning work.
2. Remove the lower unit from the outboard following manufacturer procedures.
3. Drain all gear oil and inspect for metal shavings or contamination.
4. Remove the propeller shaft and driveshaft carefully, noting orientation and sequence.
5. Clean all mating surfaces thoroughly, removing old seal material and residue.
6. Install new seals from the kit in the correct orientation, lubricating with gear oil as needed.
7. Reassemble the driveshaft and propeller shaft components in reverse order.
8. Reinstall the lower unit onto the outboard and torque all fasteners to specification.
9. Refill with the correct grade and quantity of marine gear oil.
10. Check for leaks after initial run and recheck oil level after first operating cycle.

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 oil indicating water intrusion, unusual whining or grinding noises from the gearcase, or visible oil residue around seals and shaft housings.

Will this kit fit both standard and counter-rotation models?

Yes, this seal kit is compatible with both standard and counter-rotation gear housings on the listed Mercury EFI outboards with the 2.38:1 ratio.

Do I need any special tools to install this seal kit?

Basic hand tools are required, along with a seal driver or appropriately sized socket for pressing seals into place. A torque wrench and the manufacturer's service manual are highly recommended for proper reassembly.

Can I reuse old seals if they look okay?

No. Seals are single-use components that compress and conform to their mating surfaces. Reusing old seals risks leaks and water contamination, which can cause catastrophic gearcase damage.

What type of gear oil should I use after installation?

Use Mercury Premium or High Performance Gear Lube as specified in your owner's manual. Consult your engine's documentation for the correct viscosity and capacity.

How often should gearcase seals be replaced?

Replace seals whenever the lower unit is disassembled for service, or immediately if you notice leaks or water contamination. Routine inspection every 100 hours or annually is recommended.

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.