Lower Unit Oil Drain Gasket – Fits Yamaha Outboard Motors 2.5-425HP (Replaces 90430-08020-00, 90430-08003-00)
Lower Unit Oil Drain Gasket – Fits Yamaha Outboard Motors 2.5-425HP (Replaces 90430-08020-00, 90430-08003-00) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Lower Unit Oil Drain Gasket – Fits Yamaha Outboard Motors 2.5-425HP...
Product Details
This replacement Lower Unit Oil Drain Gasket ensures a perfect seal for the gear lube drain and fill plugs on your outboard motor. It is designed for universal compatibility with all Yamaha outboard models from 1984 to the present, including all 2-stroke and 4-stroke engines from 2.5HP to 425HP.
This part is a direct replacement for Yamaha OEM part numbers 90430-08020-00 and 90430-08003-00, as well as older superseded numbers 604-45342-00-00 and 90430-08801-00.
- Installs as a direct replacement for drain and fill screw plugs.
- Engineered to prevent gear lube leaks and maintain seal integrity in harsh marine conditions.
- Made from a durable, marine-grade rubber compound.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket parts.
| Brand | Part Number | Superseded By | Notes |
|---|---|---|---|
| Yamaha | 90430-08003-00 | — | Current active part number. |
| Yamaha | 90430-08020-00 | 90430-08003-00 | Superseded part. Replaced by black gasket. |
| Yamaha | 604-45342-00-00 | 90430-08003-00 | Older superseded part number. |
| Yamaha | 90430-08801-00 | 90430-08003-00 | Older superseded part number. |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This gasket offers universal fitment for all Yamaha outboards. The models listed below are a non-exhaustive sample of confirmed compatible engines.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | All Models | 2.5–425 | 2-Stroke & 4-Stroke | 1984–Present | 90430-08003-00 | Universal Fit. Superseded 90430-08020-00. |
| Yamaha | F115, F115A, F115B | 115 | 4-Stroke | 2000–2023 | 90430-08003-00 | Two required per engine. |
| Yamaha | F150–F300 (V6) | 150–300 | 4-Stroke | 2004–2023 | 90430-08003-00 | Two required per engine. |
| Yamaha | F15–F70 | 15–70 | 4-Stroke | 1998–2023 | 90430-08003-00 | Two required per engine. |
| Yamaha | VF115–VF250 SHO | 115–250 | 4-Stroke | 2009–2023 | 90430-08003-00 | Two required per engine. |
| Yamaha | 2-Stroke Models | 9.9–300 | 2-Stroke | 1984–2012 | 90430-08003-00 | Two required per engine. |
Technical Specs
- Product Type
- Lower Unit Oil Drain Gasket
- Installation
- Direct replacement for drain and fill plugs
- Housing Material
- Marine-grade rubber compound
- Housing Color
- Black (replaces older reddish-orange version)
- Thread Size
- Compatible with standard Yamaha lower unit drain/fill plugs
- Working Pressure
- Designed for marine lower unit oil pressures
- Operating Temperature
- Suitable for all marine environment temperatures
- Function
- Prevents gear lube leaks; maintains seal integrity in marine conditions
What’s in the Box
- 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 fill/vent plug.
Installation Notes
- Position a suitable drain pan underneath the engine's lower unit.
- Using a large flathead screwdriver, carefully remove the lower drain plug screw. Allow all gear lube to drain.
- Remove the upper, oil-level fill plug screw to allow air to enter and facilitate complete draining.
- Inspect both plugs for metal shavings and clean them thoroughly.
- Remove and discard the old gaskets from both the drain and fill plugs.
- Install one new gasket onto each plug, ensuring it seats correctly.
- Using a gear lube pump, fill the lower unit through the bottom drain hole until fluid steadily flows out of the upper fill hole.
- Reinstall the upper fill plug screw with its new gasket first. Tighten securely.
- Quickly reinstall the lower drain plug screw with its new gasket and tighten securely.
- Wipe the lower unit clean and monitor the plug areas for any signs of leakage.
Troubleshooting & FAQ
How many gaskets do I need for my Yamaha outboard?
You will typically need two gaskets for a complete gear lube service: one for the lower magnetic drain plug and one for the upper oil level/fill plug.
Why did the gasket color change from red/orange to black?
Yamaha updated the material to a more durable, modern marine-grade rubber compound, which is black. This black gasket is the direct, current replacement for the older reddish-orange version and offers superior longevity.
How can I be sure this fits my specific Yamaha engine?
This gasket is designed as a universal fit for all Yamaha outboard motors manufactured from 1984 to the present, covering all horsepower ratings from 2.5HP to 425HP, both 2-stroke and 4-stroke models.
How often should these gaskets be replaced?
It is best practice to replace the drain and fill plug gaskets every time you change your lower unit gear lube. This is typically recommended annually or every 100 hours of operation, whichever comes first.
What are the signs of a failing drain plug gasket?
The most common sign of a failing gasket is a visible gear lube leak around the drain or fill plugs. You might notice an oily sheen on the water surface below your outboard or see evidence of oil dripping down the skeg.
Is this an OEM part or an aftermarket replacement?
This listing is for a high-quality aftermarket replacement part, not an OEM component. It is built to meet or exceed OEM-level specifications using comparable materials and is manufactured in an ISO 9002 certified facility with batch inspections for quality control.
What are your shipping speeds and costs?
We ship worldwide quickly, with typical transit times of 5–15 days for most regions. Standard shipping is free for most orders, and expedited options will appear at checkout if they are available for your location.
What is the warranty and return policy?
This product is covered by a 1-year warranty against manufacturing defects under normal marine use. If you encounter any issues, please contact our support team with your order details. Returns are accepted within our standard window for items that are unused and in their original condition. See our full policy page or reach out for return instructions.
Safety & Important Info
- Always verify images and specifications against your original part before purchasing. If anything differs—even if your model appears on a compatibility list—do not order.
- This is an aftermarket replacement component, not an Original Equipment Manufacturer (OEM) part.
- Professional installation by a qualified marine mechanic is recommended to ensure safety and optimal performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world reliability.
- Fast Global Fulfillment — We offer free standard delivery to most regions worldwide, with typical transit times of 5–15 days.
- Manufacturer-Direct Value — By working directly with our manufacturing partners, we provide fair pricing without compromising on materials or quality control.
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