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

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

This high-quality fiber gasket is designed to create a reliable, leak-free seal for the lower unit drain and fill plugs on Yamaha marine engines. It is compatible with a wide range of Yamaha outboard motors manufactured from 1984 to the present, including all 2-stroke and 4-stroke models.

This part is a direct replacement for multiple OEM and aftermarket part numbers, ensuring broad compatibility and a precise fit for your maintenance needs.

• Material: Constructed from a specialized, oil- and water-resistant fiber compound for a durable and secure seal.
• Installation: For optimal performance, coat the gasket and drain plug threads with fresh marine gear oil before installation.
• Function: Prevents gear oil leaks from the lower unit drain and fill screw openings.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model and 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 Yamaha P/N 90430-08003-00, 90430-08020-00)

Installation Guide

1. Position a suitable drain pan under the lower unit of your outboard motor.
2. Using the correct wrench, carefully remove the lower unit drain and vent plugs.
3. Allow the gear oil to drain completely. Inspect the old oil for any signs of metal shavings or water intrusion.
4. Remove and discard the old drain plug gaskets from both the drain and vent plugs.
5. Thoroughly clean the threads of the drain plugs and the sealing surfaces on the lower unit.
6. Apply a light coating of fresh marine gear oil to the threads of both plugs and to the new gaskets.
7. Install the new gaskets onto the drain and vent plugs.
8. Reinstall the drain and vent plugs and tighten them to the manufacturer's recommended torque specification: 7 ± 1 Nm (5.2 ± 0.7 lb-ft). Do not overtighten.
9. Refill the lower unit with the correct type and amount of gear oil through the upper vent plug hole until oil flows out, then reinstall the vent plug.
10. After running the engine, check the drain and vent plugs for any signs of leaks.

Troubleshooting & FAQ

How do I confirm this gasket fits my Yamaha engine?
This gasket is designed as a universal fit for nearly all Yamaha outboard motors (both 2-stroke and 4-stroke) made from 1984 to the present. You can verify fitment by matching your existing gasket's part number to one of the numbers listed in our Part Number Cross-Reference table.

What is the difference between part numbers 90430-08020-00 and 90430-08003-00?
Yamaha has officially superseded part number 90430-08020-00 with 90430-08003-00. They are physically and functionally identical. This aftermarket replacement is compatible with both.

How often should I replace my lower unit drain plug gaskets?
It is strongly recommended to replace the drain and vent plug gaskets every time you change your lower unit gear oil. Reusing old, compressed gaskets can lead to improper sealing and potential leaks.

What are the signs of a failed or leaking drain plug gasket?
A common sign is a visible drip or seepage of gear oil from around the drain or vent plug screw. If you notice a drop in your gearcase oil level or an oily sheen on the water beneath your motor, a faulty gasket could be the cause.

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.