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 lower unit drain plug gasket is designed to fit all Yamaha outboard motors (both 2-stroke and 4-stroke models) from 1984 to the present, providing a reliable seal for the lower unit drain and oil level screws.

It serves as a direct replacement for multiple Yamaha, Sierra, Mallory, and Mercury part numbers, ensuring wide-ranging compatibility for routine maintenance and repairs.

• Material: Made from a specialized fiber compound that is resistant to oil and water.
• Seal: Engineered to create a secure, leak-free seal when installed correctly.
• Installation: Important: Requires application of clean oil to gasket surfaces and screw threads before tightening.

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 Gasket (Replaces OEM Part 90430-08003-00 / 90430-08020-00)
• Note: Product may be sold in multi-packs by other suppliers; this listing is for a single gasket unless otherwise specified in the purchase options.

Explosion Diagram

Installation Guide

IMPORTANT: Following the correct installation procedure is critical to prevent leaks.

1. Apply clean oil to the screw threads and both surfaces of the new gasket.
2. Install the drain or oil level screw with the gasket.
3. Tighten the screw just until it is fully seated.
4. From the seated position, turn the screw an additional 45 degrees to set the final torque. Alternatively, use a torque wrench to tighten to 7 ± 1 Nm (5.2 ± 0.7 lb-ft).

NOTICE: Excessive torque and/or lack of oil on the threads and gasket surfaces could damage the gasket, resulting in an oil leak or water entering the lower unit.

Troubleshooting & FAQ

Q: How do I know if this gasket will fit my Yamaha outboard?
A: This gasket is designed for all Yamaha outboard models (2-Stroke and 4-Stroke) from 1984 to the present. You can confirm compatibility by checking your model in the "Compatible Engine Models" table or by matching your existing part number with those in the "Part Number Cross-Reference" list.

Q: What is the correct way to install this gasket to prevent leaks?
A: It is critical to apply clean engine oil to the screw threads and both surfaces of the gasket before installation. Tighten the screw until it is seated, then turn it an additional 45 degrees, or use a torque wrench to tighten to 7 ± 1 Nm (5.2 ± 0.7 lb-ft). Failure to lubricate the gasket and threads can cause damage and lead to leaks.

Q: How often should I replace my lower unit drain plug gasket?
A: It is recommended to replace the drain plug gasket every time you change your lower unit gear oil. Reusing an old, compressed gasket significantly increases the risk of oil leaks or water intrusion.

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.