90340-08002 90430-08020 Lower Unit Drain Plug Screw Kit for Yamaha | JLM Marine

90340-08002 90430-08020 Lower Unit Drain Plug Screw Kit for Yamaha | JLM Marine

This Lower Unit Drain Plug Screw Kit is designed to fit most Yamaha outboard engines from 40 HP to 300 HP. Engineered with stainless steel construction for superior corrosion resistance and longevity in marine environments, this kit ensures reliable sealing for your lower unit oil system.

This kit directly replaces OEM part numbers 90340-08002, 90430-08020, 688-45341-10-00, and several other Yamaha superseded numbers. It is essential to purchase by part number, not by engine horsepower, as fitment varies across different engine models even within the same HP range.

• Includes straight screw plug and lower unit oil drain gasket
• Stainless steel construction for maximum durability
• Direct replacement for multiple Yamaha OEM part numbers

Part Number Cross-Reference

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

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.

Important: This kit fits MOST but NOT all 40 HP to 300 HP Yamaha outboard engines. Always verify compatibility by matching your original part number before ordering.

Technical Specifications

Package Contents

This kit includes all components necessary for lower unit drain plug service:

• 1 x Straight Screw Plug (90340-08002)
• 1 x Lower Unit Oil Drain Gasket (90430-08020)

Note: The package contains all the parts shown in the product images.

Installation Guide

1. Position the outboard in an upright position and allow the lower unit to cool completely if recently operated.
2. Place a suitable drain pan beneath the lower unit to catch oil. Remove the old drain plug slowly to allow oil to drain completely.
3. Inspect the drain hole threads for damage or debris. Clean the threads with a suitable brush or cloth if necessary.
4. Remove the old gasket from the original drain plug or discard if damaged. Ensure the sealing surface around the drain hole is clean.
5. Install the new gasket (90430-08020) onto the new straight screw plug (90340-08002).
6. Thread the new drain plug by hand into the lower unit drain hole to avoid cross-threading.
7. Tighten the drain plug to the manufacturer's specified torque using a suitable wrench. Do not overtighten as this may damage threads or the gasket.
8. Refill the lower unit with the proper grade and quantity of gear oil as specified in your engine's service manual.
9. After refilling, check for leaks around the drain plug. Wipe the area clean and monitor during the first use.
10. Dispose of old gear oil properly according to local environmental regulations.

Troubleshooting & FAQ

Q: How do I confirm this drain plug kit fits my Yamaha outboard?
A: Always purchase by part number, not by horsepower rating. Cross-reference your original drain plug and gasket part numbers with those listed (90340-08002, 90430-08020, 688-45341-10-00, etc.). While this kit fits most 40-300 HP Yamaha outboards, not all models use the same drain plug design.

Q: How often should I replace the drain plug gasket?
A: Replace the gasket every time you perform a lower unit oil change to ensure a proper seal and prevent leaks. Reusing old gaskets can result in seepage or complete seal failure.

Q: What happens if I overtighten the drain plug?
A: Overtightening can strip the threads in the lower unit housing, crush the gasket excessively causing leaks, or make future removal difficult. Always tighten to the manufacturer's specified torque and use a torque wrench when possible.

Q: Can I use this plug with any type of lower unit gear oil?
A: Yes, this stainless steel drain plug and gasket are compatible with all standard lower unit gear oils. Always use the oil grade and viscosity specified in your Yamaha service manual.

Q: What are the signs that my drain plug or gasket is failing?
A: Look for visible gear oil residue around the drain plug, oil drips beneath the outboard when stored, or a low gear oil level during routine checks. Any seepage indicates the gasket should be replaced immediately.

Q: Is this an OEM part or 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.