Lower Unit Oil Seal – Fits Yamaha 40HP 70HP 80HP 100HP 4-stroke (Replaces 2807, 93101-25M03)

Product Details

This Lower Unit Oil Seal is designed for Yamaha 4-stroke outboard motors, specifically engineered to fit F40G (40HP), F70A (70HP), F80A/B (80HP), and F100A/D (100HP) models. This aftermarket propeller shaft oil seal ensures a reliable barrier against lower unit oil leaks, maintaining proper lubrication and protecting critical gearcase components.

Direct replacement for Yamaha OEM part numbers 93101-25M03 and 2807, offering a cost-effective interchange solution without sacrificing performance.

• Precision-molded to OEM dimensions for proper sealing and shaft clearance
• Designed for saltwater and freshwater marine environments
• Simple press-fit installation into lower gearcase housing

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

Application

Propeller shaft oil seal for lower gearcase unit

Material

Marine-grade elastomer compound

Fitment Type

Press-fit installation

Environment

Saltwater and freshwater compatible

What's in the Box

• 1 x Prop Shaft Oil Seal

Installation Notes

1. Drain lower unit gear oil completely and remove propeller assembly from shaft.
2. Separate lower unit from midsection following manufacturer service manual procedures.
3. Carefully remove old seal from gearcase housing using a seal puller or appropriate pick tool without damaging the bore surface.
4. Clean the seal bore thoroughly, removing all residue, corrosion, or debris.
5. Inspect the propeller shaft for scoring, wear, or damage that may compromise the new seal.
6. Lightly lubricate the new seal lip and outer diameter with marine gear oil.
7. Press the seal squarely into the bore using a seal driver or socket of appropriate diameter until fully seated.
8. Reassemble the lower unit to the midsection, ensuring proper alignment and gasket installation.
9. Refill the lower unit with the manufacturer's specified gear oil to the correct level.
10. Reinstall propeller hardware and torque to specification.
11. Run the engine briefly and inspect for leaks around the seal area.

Troubleshooting & FAQ

How do I know if my prop shaft seal needs replacement?

Common signs include visible gear oil leaking from the lower unit near the propeller, milky or contaminated gear oil indicating water intrusion, or low oil levels between service intervals. Inspect during routine maintenance or if you notice oil residue on the propeller or skeg area.

Can I install this seal without removing the lower unit?

No, proper installation requires complete lower unit removal from the midsection. The propeller shaft must be withdrawn from the gearcase to access and replace the seal. Attempting shortcuts risks improper seating and premature seal failure.

What tools do I need for installation?

You'll need a seal puller or pick set for removal, a seal driver or appropriately sized socket for installation, gear oil drain pan, torque wrench, and basic hand tools for lower unit separation. A service manual for your specific engine model is highly recommended.

Will this seal fit both saltwater and freshwater applications?

Yes, this seal is constructed from marine-grade materials designed to withstand both saltwater and freshwater environments. Ensure proper maintenance and regular lower unit oil changes to maximize seal life regardless of operating conditions.

How often should I replace the prop shaft seal?

Replace the seal whenever you observe leakage, during major lower unit service or gearcase repair, or if the lower unit has been submerged beyond normal operation. Preventive replacement every 3–5 years or during propeller shaft bearing replacement is good practice for high-use engines.

What causes premature seal failure?

Common causes include scored or damaged propeller shafts, improper installation technique, using incorrect seal drivers that damage the seal lip, debris or corrosion in the seal bore, running the lower unit with low or contaminated gear oil, and impact damage from underwater strikes.

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.