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) is backordered and will ship as soon as it is back in stock.
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Lower Unit Drain Plug Gasket – Fits Yamaha Outboard Motors (Replace...
Lower Unit Drain Plug Gasket – Fits Yamaha Outboard Motors (Replaces 90430-08003, 90430-08020) is backordered and will ship as soon as it is back in stock.
Product Details
This is a replacement Lower Unit Drain Plug Gasket designed for a universal fit across all Yamaha 2-stroke and 4-stroke outboard motors, from all HP ranges, manufactured from 1984 to the present. Made from a specialized fiber material, it ensures a secure, leak-free seal for lower unit drain and oil level screws.
It serves as a direct replacement for Yamaha part numbers 90430-08020-00, 90430-08003-00, 90430-08801-00, and 604-45342-00-00, as well as several aftermarket equivalents from Sierra and Mallory Marine.
- Engineered to resist oil and water for a durable, leak-proof seal.
- Requires oil-coating on threads and surfaces for proper installation and torque.
- Replace this gasket at every service interval to prevent contamination and leaks.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Yamaha | 90430-08020-00 | Superseded by 90430-08003-00 |
| Yamaha | 90430-08003-00 | Current Part Number |
| Yamaha | 90430-08801-00 | Interchangeable |
| Yamaha | 604-45342-00-00 | Interchangeable |
| Sierra | 18-4698 | Aftermarket Cross-Reference |
| Sierra | 18-46981-9 | Aftermarket Cross-Reference |
| Mallory Marine | 9-60100 | Aftermarket Cross-Reference |
| Mercury Marine | 27-81987M / 27-81987 | Aftermarket Cross-Reference |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This gasket fits all Yamaha outboard models with lower unit drain and oil level screws, including the following series and more.
| Brand | Model Series | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | F115 | 115 | 4-Stroke | 2000–Present | 90430-08003-00 | Supersedes 90430-08020-00 |
| Yamaha | F150/F150A/F150B/F150C | 150 | 4-Stroke | 2004–Present | 90430-08003-00 | Supersedes 90430-08020-00 |
| Yamaha | F175/F200 (2.8L) | 175-200 | 4-Stroke | 2006–Present | 90430-08003-00 | Supersedes 90430-08020-00 |
| Yamaha | F200/F225 (3.3L V6) | 200-225 | 4-Stroke | 2002–Present | 90430-08003-00 | Supersedes 90430-08020-00 |
| Yamaha | F250 (3.3L V6) | 250 | 4-Stroke | 2005–Present | 90430-08003-00 | Supersedes 90430-08020-00 |
| Yamaha | F225/F250/F300 (4.2L V6) | 225-300 | 4-Stroke | 2010–Present | 90430-08003-00 | Supersedes 90430-08020-00 |
| Yamaha | F350 | 350 | 4-Stroke | 2007–Present | 90430-08003-00 | Supersedes 90430-08020-00 |
| Yamaha | F9.9-F90 Series | 9.9-90 | 4-Stroke | All years | 90430-08003-00 | Supersedes 90430-08020-00 |
| Yamaha | T-Series (T9.9-T60) | 9.9-60 | 4-Stroke | All years | 90430-08003-00 | Supersedes 90430-08020-00 |
| Yamaha | VF Series (SHO models) | 90-250 | 4-Stroke | 2009–Present | 90430-08003-00 | Supersedes 90430-08020-00 |
| Yamaha | 2-Stroke Models | All | 2-Stroke | 1984–Present | 90430-08003-00 | Supersedes 90430-08020-00 |
Technical Specs
- Product Type
- Lower Unit Drain Plug Gasket
- Material
- Specialized Fiber
- Color
- Black
- Thread Size
- Compatible with 90340-08002-00 and similar drain plugs
- Recommended Torque
- 7 ± 1 Nm (0.7 ± 0.1 m-kgf, 5.2 ± 0.7 lb-ft)
- Installation
- Oil-coated threads and surfaces required
- Key Attributes
- Oil and water resistant; provides secure, leak-free seal
What’s in the Box
- 1 x Lower Unit Drain Plug Gasket (Replaces 90430-08003-00)
Installation Notes
IMPORTANT: Proper installation is critical to prevent leaks and damage. Always use a new gasket for each service.
- Apply clean marine gear oil to the screw threads and to both surfaces of the new gasket.
- Install the drain or oil level screw with the lubricated gasket.
- Tighten the screw to the specified torque: 7 ± 1 Nm (5.2 ± 0.7 lb-ft). Alternatively, tighten until the gasket is seated, then turn an additional 45 degrees.
NOTICE: Failure to lubricate the gasket and threads or applying excessive torque can crush the gasket, causing an oil leak or allowing water to enter the lower unit.
Troubleshooting & FAQ
How do I know if this gasket fits my motor?
This gasket is designed for a universal fit on virtually all Yamaha outboard motors (2-stroke and 4-stroke) made from 1984 to present. To be certain, you can cross-reference your old gasket's part number with the numbers in our Part Number Matrix or check your model in the compatibility table.
Can I reuse my old gasket?
No. These are single-use crush gaskets. They are designed to compress and create a seal once. Reusing an old gasket significantly increases the risk of an oil leak or water intrusion into your gearcase, which can lead to catastrophic failure.
What happens if I don't use oil on the gasket during installation?
Applying oil to the gasket surfaces and screw threads is a required step. The lubrication allows the gasket to compress correctly and achieve a proper seal at the specified torque. Installing it dry can cause the gasket to bind and tear, resulting in an improper seal and leaks.
What are the signs of a failed drain plug gasket?
The most common sign is a visible drip of gear lube from the lower unit drain screw. Another symptom is "milky" or cloudy gear lube when you drain it, which indicates that water has entered the gearcase through a failed seal.
What is the correct replacement interval?
You must replace the lower unit drain and fill gaskets every time you remove the corresponding screws. This should be done at every scheduled lower unit service or oil change.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost?
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns?
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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