Lower Unit Oil Drain Gasket – Fits Yamaha Outboard Motors (Replaces 90430-08003, 90430-08020)
Lower Unit Oil Drain 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 Oil Drain Gasket – Fits Yamaha Outboard Motors (Replaces...
Lower Unit Oil Drain 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 Lower Unit Oil Drain Gasket – Fits Yamaha Outboard Motors (Replaces 90430-08003, 90430-08020) creates a secure, leak-free seal for the lower unit drain and oil level screws. It is designed for a broad range of Yamaha outboards, covering all 2.5–350 HP models (both 2-Stroke and 4-Stroke) from 1984 to the present.
It serves as a direct replacement for Yamaha parts 90430-08020-00, 90430-08003-00, 90430-08801-00, and 604-45342-00-00, and interchanges with Sierra 18-4698, Mallory 9-60100, and Mercury 27-81987M.
- Engineered from a specialized fiber material for superior oil and water resistance.
- Forms a reliable seal when torqued to the manufacturer's specification of 7 ± 1 Nm.
- Requires oil-coated threads and surfaces for proper installation and sealing.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket brands.
| Brand | Part Number |
|---|---|
| Yamaha | 90430-08020-00 |
| Yamaha | 90430-08003-00 |
| Yamaha | 90430-08801-00 |
| Yamaha | 604-45342-00-00 |
| Sierra | 18-4698 |
| Sierra | 18-46981-9 |
| Mallory Marine | 9-60100 |
| Mercury Marine | 27-81987M |
| Mercury Marine | 27-81987 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Yamaha engines, this gasket fits nearly all models manufactured from 1984 to present. The following table provides a detailed list of compatible series.
| 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 3/8"-16 drain plugs
- Installation Torque
- 7 ± 1 Nm (5.2 ± 0.7 lb-ft)
- Other Technical Attributes
- Oil and water resistant; provides secure, leak-free seal
What’s in the Box
- 1 x Lower Unit Oil Drain Gasket (Replaces OEM 90430-08003-00 & 90430-08020-00)
Installation Notes
- Place a suitable oil drain pan under the lower unit drain screw.
- Remove the lower unit drain screw and the old gasket.
- Clean the threads of the drain screw and the mating surface on the gearcase.
- Lightly coat the new gasket and the screw threads with fresh gear lube.
- Install the new gasket onto the screw and thread it into the gearcase.
- Tighten the screw to the manufacturer's recommended torque: 7 ± 1 Nm (5.2 ± 0.7 lb-ft). Do not overtighten.
- Proceed with filling the lower unit with oil per your owner's manual instructions.
- After filling, check for any leaks around the drain screw.
Troubleshooting & FAQ
How often should this drain plug gasket be replaced?
This gasket should be replaced every time you change your lower unit gear oil. Reusing an old, compressed gasket significantly increases the risk of a leak, which can lead to catastrophic gearcase failure.
What are the signs of a failing drain plug gasket?
The most common sign is a visible oil drip or seepage from the lower unit drain screw. You may also notice a milky or light coffee color in your gear oil when you drain it, which indicates water intrusion from a failed seal.
Amazon reviews for similar parts mention fitment issues. Are these guaranteed to fit?
While this aftermarket gasket is designed to meet or exceed OEM specifications for all listed Yamaha models, variations in manufacturing tolerances can occasionally occur. We recommend carefully comparing the new gasket to your old one before installation. If it appears different, do not install it. Our parts are batch-inspected for consistency and backed by our warranty.
What is the difference between this and the OEM Yamaha part?
This listing is an aftermarket replacement (not OEM). It is built to OEM-level specifications with comparable materials for a fraction of the price. We ensure our parts are manufactured in an ISO 9002 facility and are batch-inspected for consistency and quality.
How fast is shipping and what does it cost?
We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free for most regions; expedited options and final costs are shown at checkout where available.
What is your warranty and return policy?
This product is covered by a 1-year warranty against manufacturing defects under normal use. If you encounter an issue, please contact our support team with your order details. Returns are accepted within our standard window for unused items in their original condition. See our policy page or reach out for instructions.
Safety & Important Info
- Verify images and specifications against your original part before purchasing. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement part, not an OEM component. All mentions of brand names and part numbers are for reference purposes only.
- Professional installation is highly recommended for safety and to ensure proper performance. Failure to follow service manual procedures can lead to equipment damage or personal injury.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world conditions.
- Fast Global Fulfillment — We offer free standard delivery to most regions, with typical transit times of 5–15 days.
- Manufacturer-Direct Value — By working directly with manufacturers, we provide fair pricing without compromising on materials or quality control.
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