Lower Unit Oil Drain Gasket – Fits Yamaha Outboard Motors (Replaces 90430-08003, 90430-08020)

Lower Unit Oil Drain Gasket – Fits Yamaha Outboard Motors (Replaces 90430-08003, 90430-08020)

This lower unit oil drain gasket is designed for a precise fit on a wide range of Yamaha Outboards, including all models from 2.5 HP to 350 HP (2-Stroke & 4-Stroke) manufactured from 1984 to the present. It creates a secure, leak-free seal for both the lower unit drain and oil level screws, preventing oil leaks and water intrusion.

This component is a direct replacement for multiple OEM and aftermarket part numbers, ensuring broad compatibility and a reliable alternative to factory originals.

• Critical Seal: Creates a secure seal for the lower unit drain and oil level screws.
• Installation Requirement: For best results, coat the gasket and screw threads with a thin layer of oil before installation.
• Material: Made from a specialized, high-density fiber that is resistant to oil and water.

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

• 1x Gasket (Replaces OEM Part Numbers 90430-08003-00 and 90430-08020-00)

Installation Guide

1. Place a suitable drain pan under the lower unit drain screw.
2. Using a proper screwdriver or wrench, remove the lower drain screw, followed by the upper oil level screw to vent the gearcase.
3. Allow all the old gear oil to drain completely. Inspect the oil for any signs of water (milky appearance) or metal shavings.
4. Clean the drain screw and the sealing surface on the gearcase, removing any remnants of the old gasket.
5. Lightly coat the new gasket and the drain screw threads with fresh marine gear oil.
6. Install the new gasket onto the drain screw.
7. Reinstall the lower drain screw and tighten it to the specified torque: 7 ± 1 Nm (5.2 ± 0.7 lb-ft). Do not overtighten.
8. Fill the gearcase with the recommended gear lubricant through the upper oil level hole until fluid begins to run out of the hole.
9. Reinstall the upper oil level screw with its gasket and tighten securely.

Troubleshooting & FAQ

Q: How do I confirm this gasket fits my specific engine?
A: The best way is to check the part number on your old gasket or in your engine's service manual. You can then cross-reference it with the numbers in our "Part Number Cross-Reference" table. Also, verify your engine model and year are listed in the "Compatible Engine Models" table.

Q: I installed the gasket, but it still leaks. What should I do?
A: First, ensure the drain screw was tightened to the correct torque specification of 7 ± 1 Nm (5.2 ± 0.7 lb-ft). Overtightening can damage the gasket, while undertightening will not create a proper seal. Also, check the sealing surface on your gearcase for any nicks, scratches, or debris that could prevent a flush fit. If issues persist, please contact our support team for assistance.

Q: How often should I replace my lower unit drain gaskets?
A: It is highly recommended to use a new gasket every time you change your lower unit gear oil. Gaskets compress during installation and are considered a single-use item to ensure a reliable, leak-proof seal.

Q: The gasket I received seems slightly different in size from my original. Will it still work?
A: While we design our parts to meet OEM specifications, minor variations can occur in aftermarket manufacturing. Please ensure the part you received matches the product images and specifications. If you believe there is a significant discrepancy or fitment issue, do not install the part and contact us for support.

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.