Lower Unit Oil Seal – Fits Yamaha 50-100 HP (Replaces 93101-25M03-00)
Lower Unit Oil Seal – Fits Yamaha 50-100 HP (Replaces 93101-25M03-00) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Lower Unit Oil Seal – Fits Yamaha 50-100 HP (Replaces 93101-25M03-00) is backordered and will ship as soon as it is back in stock.
Product Details
This is a replacement Lower Unit Oil Seal – Fits Yamaha 50-100 HP Outboards (Replaces 93101-25M03-00). It is designed for various Yamaha 50-100 HP 2-stroke and 4-stroke outboard models, serving as a critical component in the gearcase to prevent water intrusion and oil leakage. This S-type seal measures 25×40×6 mm, ensuring a precise fit for the driveshaft or propshaft application.
This component is a direct replacement for Yamaha OEM part number 93101-25M03-00 and is interchangeable with Sierra 18-0587. It is also the same seal included in service kits from REPLACEMENTKITS.COM and SupremeMarine.
- Installation Location: Mounts in the lower unit gearcase assembly.
- Material: Constructed from durable rubber with a metal spring reinforcement for a reliable seal.
- Quantity: Note that two seals are typically required per lower unit for a complete service.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Yamaha | 93101-25M03-00 | OEM Reference |
| Sierra | 18-0587 | Aftermarket Interchange |
| REPLACEMENTKITS.COM | Kit | Includes this seal |
| SupremeMarine | 9310125M03 Kit | Includes this seal |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This seal is confirmed to fit various Yamaha 50-100 HP 2-Stroke & 4-Stroke outboards requiring part number 93101-25M03-00. Due to a lack of specific model and year data, please verify the dimensions (25mm x 40mm x 6mm) and part number against your service manual before ordering.
Technical Specs
- Product Type
- Lower Unit Oil Seal (S-Type)
- Installation
- Lower Unit/Gearcase
- Dimensions
- 25 mm × 40 mm × 6 mm (inner × outer × width)
- Material
- Rubber with metal spring reinforcement
- Seal Type
- S-Type
- Color
- Black
- OEM Part Number
- 93101-25M03-00
- Application
- Driveshaft/Propshaft Seal
- Quantity Per Engine
- 2 seals typically required per lower unit
What’s in the Box
- When purchased individually: 1 x S-Type Oil Seal (93101-25M03-00)
- When purchased as a kit: Contents vary by manufacturer (typically includes 2 seals per kit)
Installation Notes
- Drain the lower unit gearcase oil completely.
- Remove the propeller and any related hardware.
- Unbolt and remove the propshaft bearing housing from the gearcase.
- Carefully pry out the old oil seals from the housing, noting their orientation.
- Clean the seal housing thoroughly, ensuring there is no debris or corrosion.
- Lightly grease the new seals and the housing surface.
- Press the new seals into the housing, ensuring they are seated squarely and in the correct orientation (springs typically face the oil).
- Reinstall the bearing housing, propeller, and all hardware, torquing bolts to manufacturer specifications.
- Refill the lower unit with fresh gear lube to the correct level.
Troubleshooting & FAQ
How do I know if my oil seal is failing?
The most common sign is milky or cloudy gear lube, which indicates water has entered the lower unit. Other signs include visible oil leaks around the prop shaft or bearing carrier, or finding fishing line wrapped around the shaft, which can cut the seal.
How many seals do I need for a lower unit service?
Most Yamaha lower units require two seals for the propshaft assembly. However, always consult your engine's service manual to confirm the exact quantity and part numbers before starting work.
Is this oil seal directional?
Yes. The side of the seal with the visible spring is designed to face the fluid it is sealing in (the gear oil). Installing it backwards will result in a leak. Make note of the old seal's orientation before removal.
What are the signs of incorrect installation?
An incorrectly installed seal will leak almost immediately. After refilling the gearcase with lube, check for drips around the propeller shaft area. A milky appearance in the gear lube after a short run time also indicates a leak.
ractice to replace these seals whenever servicing the water pump impeller or pressure testing the gearcase, which is often recommended every 1-3 years depending on saltwater or freshwater usage.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 vs 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.
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