27-8M0089639 Lower Unit Seal Kit for Mercury Mariner 25HP 30HP | JLM Marine

Lower Unit Seal Kit – Fits Mercury Mariner 25-30HP 2-Stroke Outboards

This lower unit seal kit is designed for Mercury Mariner 2-cylinder, 2-stroke outboards rated at 25HP and 30HP, including Jet models. It provides a complete sealing solution for lower unit maintenance and rebuilds on international models from serial number 0N055505 and up.

This aftermarket replacement directly crosses to OEM part numbers 27-8M0089639, 27-8M0089636, 95220A1, and 804908A01, ensuring compatibility across multiple Mercury Mariner service part references.

• Complete seal kit with gasket for lower unit service
• Fits 2-cylinder, 2-stroke 25HP and 30HP models (including Jet configurations)
• Direct replacement for multiple OEM part numbers

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

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.

Technical Specifications

Package Contents

This kit includes the following components:

• 1 x Lower Unit Seal Kit with Gasket

Installation Guide

1. Disconnect the outboard from the power source and secure the motor in a stable position. Remove the lower unit from the gear housing following your service manual.
2. Drain all gear oil completely and inspect for contamination or metal debris. Clean all mating surfaces thoroughly with a suitable solvent.
3. Remove the old seals, gaskets, and O-rings from the lower unit housing. Inspect bearing surfaces and shift components for wear or damage.
4. Install new seals from the kit using a seal driver or appropriately sized socket. Ensure each seal seats squarely without cocking or distortion.
5. Apply a thin layer of marine-grade grease to seal lips before assembly. Position the new gasket carefully, ensuring all bolt holes align.
6. Reassemble the lower unit to the gear housing, torquing all fasteners to manufacturer specifications. Refill with the correct grade and quantity of gear oil.
7. Check for proper shift engagement and smooth operation before returning the outboard to service. Test run and inspect for leaks.

Troubleshooting & FAQ

Q: How do I confirm this seal kit fits my Mercury Mariner outboard?
A: Verify your engine model, HP rating, and serial number against the compatibility table above. Models must be 2-cylinder, 2-stroke, 25HP or 30HP (including Jet) with serial numbers 0N055505 and up (0N088578 for Jet models). Cross-reference your current seal kit part number with 27-8M0089639, 27-8M0089636, 95220A1, or 804908A01.

Q: What are the signs that my lower unit seals need replacement?
A: Common symptoms include gear oil leaking from the lower unit, water contamination in the gear oil (milky appearance), difficulty shifting gears, or unusual noise from the lower unit during operation. Regular inspection during seasonal maintenance is recommended.

Q: How often should I replace lower unit seals?
A: Replace seals during lower unit rebuilds, whenever the lower unit is disassembled for service, or if you observe leaks or water intrusion. Many mechanics recommend inspecting seals annually and replacing them every 2-3 years or 200-300 hours of operation, depending on usage conditions.

Q: Can I use this aftermarket seal kit instead of the OEM Mercury part?
A: Yes, this aftermarket seal kit is manufactured to OEM specifications and provides equivalent sealing performance. It directly replaces OEM part numbers 27-8M0089639, 27-8M0089636, 95220A1, and 804908A01. Many marine technicians use quality aftermarket seals for routine maintenance and rebuilds.

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?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.