Lower Unit Oil Seal – Fits Yamaha 50-100 HP Outboards (Replaces 93101-25M03-00)

Lower Unit Oil Seal – Fits Yamaha 50-100 HP Outboards (Replaces 93101-25M03-00)

This lower unit oil seal is engineered for Yamaha 50-100 HP 2-Stroke & 4-Stroke outboards that utilize a 25×40×6 mm S-type seal. It serves as a direct-fit replacement, ensuring a reliable barrier against water intrusion and oil leaks in the gearcase.

This component is a direct replacement for Yamaha part number 93101-25M03-00 and Sierra 18-0587. It is also the same seal included in aftermarket kits from REPLACEMENTKITS.COM and SupremeMarine.

• Dimensions: 25 mm (inner) × 40 mm (outer) × 6 mm (width)
• Material: High-grade rubber with a metal spring reinforcement for a secure, long-lasting seal.
• Application: Designed for use as a driveshaft and/or propshaft seal in the lower unit.

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 Yamaha owners, here’s a guide to help you identify your engine’s serial/model: Yamaha Serial Number Guide. You can also review exploded diagrams to verify part numbers: Yamaha Parts Diagrams & Catalog.

Technical Specifications

Package Contents

Package contents depend on the purchase option:

• Individual Part: 1 x S-Type Oil Seal (Replaces 93101-25M03-00)
• Aftermarket Kits: Contents vary. Most kits typically include two seals per package. Please verify the contents of the specific kit you are purchasing.

Installation Guide

1. Drain Oil: Start by completely draining the gearcase oil into a suitable container.
2. Remove Propeller & Lower Unit: Remove the propeller assembly. Then, unbolt and carefully detach the entire lower unit from the outboard's midsection.
3. Access Seals: Secure the lower unit on a workbench to easily access the driveshaft and propeller shaft housings.
4. Extract Old Seals: Carefully pry out the old oil seals using a seal puller or flat-head screwdriver. Take note of their orientation.
5. Clean Housing: Thoroughly clean the seal seating area inside the housing. Remove any old sealant, dirt, or corrosion.
6. Lubricate New Seals: Apply a light coat of marine grease to the inner and outer surfaces of the new oil seals.
7. Install Seals: Press the new seals into the housing using a seal driver or a socket of the appropriate diameter. Ensure they are seated evenly and facing the correct direction (typically, the spring side faces the oil).
8. Reassemble: Re-install the lower unit, torquing the bolts to the manufacturer's specifications.
9. Refill Gear Lube: Fill the gearcase with the recommended marine gear lubricant.
10. Check for Leaks: Before operating the outboard, check for any signs of oil leaks around the newly installed seals.

Troubleshooting & FAQ

How do I know if this oil seal will fit my Yamaha outboard?
This seal is designed for most Yamaha 50-100 HP 2-Stroke and 4-Stroke outboards. The most reliable way to confirm fitment is by matching the OEM part number 93101-25M03-00 or the dimensions 25mm x 40mm x 6mm to your existing seal.

What are the signs of a failing lower unit oil seal?
Common signs include a milky or cloudy appearance in your gear lube (indicating water intrusion), visible oil leaking from the propeller shaft area, or fishing line tangled around the propshaft, which can damage the seal.

How many seals do I need for a complete lower unit service?
A typical lower unit service requires two of these seals—one for the driveshaft and one for the propeller shaft. We recommend replacing both simultaneously, but you should always verify your specific engine's requirements.

OEM vs. Aftermarket?
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.

How fast do you ship and how much does it cost?
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.

What is your warranty and return policy?
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.