Lower Unit Oil Drain Gasket – Fits Yamaha Outboard Motors (Replaces 90430-08020-00, 90430-08003-00)

Lower Unit Oil Drain Gasket – Fits Yamaha Outboard Motors (Replaces 90430-08020-00, 90430-08003-00)

This lower unit oil drain gasket provides a direct replacement for all Yamaha outboard motors from 1984 to the present, including models from 2.5HP to 425HP (both 2-Stroke and 4-Stroke). It ensures a tight seal for both the drain and fill plugs, preventing gear lube leaks.

This part replaces Yamaha OEM part numbers 90430-08020-00 and 90430-08003-00. It also supersedes older part numbers 604-45342-00-00 and 90430-08801-00.

• Fitment: Universal compatibility with all Yamaha outboards (1984-Present).
• Function: Seals the lower unit drain and fill plugs to prevent leaks.
• Material: Constructed from a durable, marine-grade rubber compound.

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

• 1 x Lower Unit Drain Gasket (Replaces 90430-08003-00 / 90430-08020-00)

Note: Two gaskets are typically required per engine service—one for the oil drain plug and one for the oil fill (vent) plug.

Installation Guide

Always consult your owner's service manual for instructions specific to your engine model. The general process is as follows:

1. Position a suitable oil drain pan under the lower unit.
2. Using a large flathead screwdriver or appropriate tool, loosen and remove the lower drain plug screw.
3. Loosen and remove the upper oil level (vent) plug screw to allow the gear lube to drain completely.
4. Remove the old gaskets from both plug screws. Clean the plugs and the sealing surfaces on the gearcase.
5. Place a new gasket onto the drain plug screw and reinstall it. Do not overtighten.
6. Fill the lower unit with the manufacturer's recommended gear lube through the bottom drain hole until it begins to flow out of the upper vent hole.
7. Install the new gasket on the upper vent plug screw and reinstall the screw.
8. Quickly remove the gear lube filler tube and reinstall the lower drain plug screw. Tighten both screws securely.

Troubleshooting & FAQ

Q: How do I know if this gasket will fit my Yamaha outboard?
A: This gasket is designed for universal fitment across all Yamaha outboard motors (2.5HP to 425HP, 2-stroke and 4-stroke) manufactured from 1984 to the present. It is a direct replacement for OEM part numbers 90430-08020-00 and 90430-08003-00.

Q: How many gaskets do I need for a complete gear lube change?
A: You will need two gaskets per engine. One is for the magnetic lower drain plug, and the other is for the upper fill/vent plug.

Q: The original gasket on my engine was reddish-orange, but this one is black. Is it the correct part?
A: Yes. Yamaha has superseded the older reddish-orange gasket (90430-08020-00) with this updated black version (90430-08003-00). It is the correct replacement and offers the same or better sealing performance.

Q: How often should I replace these gaskets?
A: It is strongly recommended to use a new gasket every time you change your lower unit gear lube. Reusing a crushed gasket can lead to leaks and water intrusion, which can cause catastrophic gearcase failure.

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.