Yamaha Outboard Lower Unit Drain Gasket - Fits Yamaha Marine Engines (Replaces 90430-08003-00)

Yamaha Outboard Lower Unit Drain Gasket – Fits Yamaha Marine Engines

This replacement lower unit drain gasket is designed for universal fitment across all Yamaha Marine 2-stroke and 4-stroke outboard engines from 1985 to the current model year, covering all horsepower ranges. It serves as a direct, high-quality seal for both the lower unit drain plug and the vent plug.

Engineered to meet or exceed OEM specifications, this gasket ensures a secure, leak-free seal when servicing your outboard's lower unit. It directly replaces Yamaha part numbers 90430-08003-00, 90430-08020-00, 90430-08801-00, and Sierra 18-4698.

• Installation: The gasket is placed between the drain/vent plug and the lower unit housing to create a seal.
• Material: Made from a durable black rubber compound, updating the older reddish-orange material.
• Compatibility: Universal fit for all Yamaha outboard models (2-350 HP, 1985–Current).

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 Drain Plug Gasket (Replaces 90430-08003-00)
• Note: Yamaha recommends purchasing two gaskets when servicing an outboard, as this gasket is used for both the drain plug and vent plug locations.

Installation Guide

1. Place a suitable drain pan under the lower unit.
2. Using a large flathead screwdriver or appropriate tool, carefully unscrew and remove the lower magnetic drain plug.
3. Unscrew and remove the upper vent plug located above the drain plug to allow air to enter and oil to flow out smoothly.
4. Allow the gearcase oil to drain completely. Inspect the oil's color and for any metallic debris on the magnetic plug.
5. Remove the old gasket from both the drain plug and the vent plug. Discard the old gaskets.
6. Clean the plug threads and the sealing surface on the lower unit housing.
7. Install a new gasket onto both the drain plug and the vent plug.
8. Fill the lower unit with the manufacturer-specified gear lube through the bottom drain hole until lube begins to flow out of the upper vent hole.
9. First, reinstall the upper vent plug with its new gasket and tighten it securely.
10. Quickly reinstall the lower drain plug with its new gasket and tighten it to the specified torque.
11. Wipe the area clean and monitor for any leaks.

Troubleshooting & FAQ

Q: How do I confirm this gasket fits my engine?
A: This gasket is designed for universal fitment on all Yamaha 2-stroke and 4-stroke outboard models from 1985 to present, across all horsepower ranges (2-350 HP). It directly replaces OEM part number 90430-08003-00.

Q: Why is this gasket black when my old one was reddish-orange?
A: This gasket is made from a modern, durable black rubber compound. It is the direct successor to the previous reddish-orange colored material and offers equivalent or superior sealing performance.

Q: Do I need to buy one or two gaskets?
A: It is highly recommended to purchase two gaskets. Yamaha outboards use this same gasket for both the lower unit drain plug and the upper oil level vent plug. Both should be replaced during a gear lube change.

Q: How often should I replace this drain plug gasket?
A: You should replace the drain and vent plug gaskets every time you change your lower unit gear lube, which is typically recommended once per season or every 100 hours of operation, whichever comes first.

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.