Lower Unit Oil Drain Plug Gasket – Fits Yamaha Outboard Motors (Replaces 90430-08003-00, 90430-08020-00)
Lower Unit Oil Drain Plug Gasket – Fits Yamaha Outboard Motors (Replaces 90430-08003-00, 90430-08020-00) is backordered and will ship as soon as it is back in stock.
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Lower Unit Oil Drain Plug Gasket – Fits Yamaha Outboard Motors (Rep...
Lower Unit Oil Drain Plug Gasket – Fits Yamaha Outboard Motors (Replaces 90430-08003-00, 90430-08020-00) is backordered and will ship as soon as it is back in stock.
Product Details
This Lower Unit Oil Drain Plug Gasket – Fits Yamaha Outboard Motors (Replaces 90430-08003-00, 90430-08020-00) provides a reliable, leak-free seal for the lower unit drain and fill plugs. It is designed for a wide range of Yamaha outboard motors, including both 2-Stroke and 4-Stroke models, from 1984 to the present.
This part serves as a direct replacement for Yamaha 90430-08020-00, 90430-08003-00, 90430-08801-00, 604-45342-00-00; Mercury Marine 27-81987, 27-81987M; Sierra 18-4698, 18-46981-9; and Mallory Marine 9-60100.
- Provides a secure, leak-free seal resistant to oil and water.
- Requires oil-coating on threads and surfaces before installation.
- Replaces earlier reddish-orange versions with a durable black specialized fiber material.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 90430-08020-00 |
| Yamaha | 90430-08003-00 |
| Yamaha | 90430-08801-00 |
| Yamaha | 604-45342-00-00 |
| Mercury Marine | 27-81987 |
| Mercury Marine | 27-81987M |
| Sierra | 18-4698 |
| Sierra | 18-46981-9 |
| Mallory Marine | 9-60100 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Yamaha engines, this gasket fits a wide range of 2-stroke and 4-stroke models from 1984 to the present. Please verify your specific model in the list.
| 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 (replaces earlier reddish-orange versions)
- Thread Size
- Compatible with 3/8"-16 drain plugs
- Installation
- Oil-coated threads and surfaces required
- Working Torque
- 7 ± 1 Nm (0.7 ± 0.1 m-kgf, 5.2 ± 0.7 lb-ft)
- Operating Temperature
- -40°C to 120°C (-40°F to 248°F)
- Other Attributes
- Oil and water resistant; provides secure, leak-free seal
- Warranty
- 1 Year (varies by seller)
What’s in the Box
- 1 x Lower Unit Drain Plug Gasket (Replaces 90430-08003-00)
Note: For a complete gear oil change, two gaskets are typically required—one for the lower drain plug and one for the upper fill plug.
Installation Notes
- Position a drain pan under the lower unit.
- Remove the lower drain plug and old gasket, allowing the oil to drain completely.
- Clean the plug and the sealing surface on the gearcase.
- Lightly coat the threads of the drain plug and both sides of the new gasket with fresh gear lube.
- Install the new gasket and tighten the plug to the specified torque (7 ± 1 Nm / 5.2 ± 0.7 lb-ft). Do not overtighten.
- Remove the upper fill plug and fill with the correct gear oil until it flows out of the upper vent hole.
- Install the upper plug with a new gasket and tighten securely.
Troubleshooting & FAQ
How often should I replace this gasket?
It is best practice to replace the drain plug gasket with every gear oil change to ensure a proper, leak-free seal. Reusing old gaskets increases the risk of oil leaks or water intrusion.
What are the signs of a failing drain plug gasket?
Signs of failure include visible gear oil leakage around the drain plug, a milky or creamy appearance in the gear oil (indicating water has entered the gearcase), or a gasket that appears cracked, brittle, or overly compressed upon inspection.
My old gasket was reddish-orange. Why is this one black?
This black fiber gasket is the newer, updated version that supersedes the earlier reddish-orange models. It is made from a modern, specialized fiber material that offers equivalent or superior sealing performance and durability.
Does this gasket fit both the drain and fill plugs?
Yes, on most compatible Yamaha models, the same gasket is used for both the lower oil drain plug and the upper oil level (fill) plug. Two gaskets are usually needed for a complete gear oil service.
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.
LETSafety & 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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