Lower Unit Oil Drain Plug Gasket for Yamaha Outboard Motors – Replaces 90430-08003-00 and 90430-08020-00
Lower Unit Oil Drain Plug Gasket for Yamaha Outboard Motors – Replaces 90430-08003-00 and 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 for Yamaha Outboard Motors – Repla...
Lower Unit Oil Drain Plug Gasket for Yamaha Outboard Motors – Replaces 90430-08003-00 and 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 is an aftermarket replacement sealing washer for compatible Yamaha outboard gearcase drain and fill plugs. It is intended to help create a secure seal during lower-unit gear-oil service and replace worn, compressed, or damaged gaskets.
The primary Yamaha reference numbers associated with this replacement are 90430-08003-00 and 90430-08020-00. Additional reference numbers are listed below for comparison only. Always compare the original gasket, plug, engine model, and applicable parts information before ordering.
- Designed for lower-unit drain and fill plug sealing applications.
- Helps reduce the risk of gear-oil leakage and water intrusion when correctly installed.
- Suitable for replacement during routine lower-unit gear-oil service.
- Replace the gasket rather than reusing a visibly compressed or damaged sealing washer.
Part Number Matrix
The following OEM and aftermarket numbers are reference identifiers associated with this gasket application. They do not by themselves confirm fitment for every engine model.
| 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 and Model Compatibility
This gasket is listed for use across a broad range of Yamaha outboard applications, including selected 2-stroke and 4-stroke models. The model groups below are examples of the applications associated with the listed reference numbers and are not a substitute for checking the exact model code, year, serial range, and gearcase parts diagram.
| Brand | Model Series | Rated HP | Stroke | Years | Reference Part No. | Verification Note |
|---|---|---|---|---|---|---|
| Yamaha | F115 | 115 | 4-Stroke | 2000–Present | 90430-08003-00 | Verify exact model and serial range. |
| Yamaha | F150/F150A/F150B/F150C | 150 | 4-Stroke | 2004–Present | 90430-08003-00 | Verify exact model and serial range. |
| Yamaha | F175/F200, 2.8L applications | 175–200 | 4-Stroke | Application dependent | 90430-08003-00 | Check the applicable parts diagram. |
| Yamaha | F200/F225, 3.3L V6 applications | 200–225 | 4-Stroke | Application dependent | 90430-08003-00 | Check the applicable parts diagram. |
| Yamaha | F250, 3.3L V6 applications | 250 | 4-Stroke | Application dependent | 90430-08003-00 | Check the applicable parts diagram. |
| Yamaha | F225/F250/F300, 4.2L V6 applications | 225–300 | 4-Stroke | Application dependent | 90430-08003-00 | Check the applicable parts diagram. |
| Yamaha | F350 | 350 | 4-Stroke | Application dependent | 90430-08003-00 | Check the applicable parts diagram. |
| Yamaha | F9.9–F90 series | 9.9–90 | 4-Stroke | Application dependent | 90430-08003-00 | Check the applicable parts diagram. |
| Yamaha | T9.9–T60 series | 9.9–60 | 4-Stroke | Application dependent | 90430-08003-00 | Check the applicable parts diagram. |
| Yamaha | VF series | 90–250 | 4-Stroke | Application dependent | 90430-08003-00 | Check the applicable parts diagram. |
| Yamaha | Selected 2-stroke models | Model dependent | 2-Stroke | Application dependent | 90430-08003-00 | Confirm the exact model and serial range. |
Technical Specifications
- Product Type
- Lower-unit oil drain and fill plug gasket
- Application
- Outboard gearcase gear-oil service
- Material
- Specialized fiber sealing material
- Color
- Black
- Reference Thread Application
- Associated with compatible 3/8-16 drain-plug applications; verify the plug and gasket dimensions before installation.
- Quantity
- One gasket
- Brand Type
- Aftermarket replacement; not a Yamaha-branded OEM component
What's in the Box
- 1 × Lower-unit oil drain plug gasket
Many gear-oil changes use two gaskets: one for the lower drain plug and one for the upper fill or vent plug. Confirm the requirement for your specific gearcase before beginning service.
Installation Notes
- Place a suitable drain pan beneath the lower unit.
- Remove the lower drain plug and old gasket, then allow the gear oil to drain completely.
- Clean the plug and the gearcase sealing surface. Remove old gasket material and debris.
- Install the new gasket in the correct position. If specified by the engine manufacturer, lightly lubricate the gasket and plug threads with the appropriate gear lubricant.
- Start the plug by hand to avoid cross-threading, then tighten it using the torque specification in the applicable engine service information. Do not overtighten.
- Refill the gearcase with the correct gear lubricant according to the engine manufacturer's service procedure.
- Install the fill plug with a new gasket when required, then inspect both plugs for leakage after servicing.
Troubleshooting and FAQ
How often should this gasket be replaced?
Replacement at each gear-oil change is good service practice because the gasket may compress during installation. Replace it immediately if it is cracked, deformed, damaged, or leaking.
What are the signs of a failing drain-plug gasket?
Common signs include gear-oil seepage around the plug, a damaged or flattened gasket, or water contamination in the gearcase oil. A milky appearance in the drained oil should be investigated before the engine is returned to service.
Can one gasket be used for both the drain and fill plugs?
On compatible applications, the same gasket may be used at both plugs. Check the exact gearcase parts diagram and plan on two gaskets when the service procedure requires one at each plug.
Is this an OEM Yamaha part?
No. This listing is for an aftermarket replacement gasket. The Yamaha numbers shown are reference numbers used to help identify the intended application.
How do I confirm fitment?
Match the original gasket and plug, then verify the engine brand, model, horsepower, stroke, year, serial range, and gearcase parts diagram. Do not rely on horsepower or a general model family alone.
Safety and Important Information
- Use the correct gear lubricant and follow the service procedure for your exact engine.
- Do not force the plug or overtighten it; damaged threads can cause leaks or gearcase damage.
- Inspect the old oil for water contamination and check for leaks after installation.
- Verify the part number, dimensions, and application before purchase and installation.
- Professional installation is recommended when the correct procedure or torque specification is uncertain.
About Sea Sierra
- Marine Replacement Parts — Practical replacement components for common marine service applications.
- Application-Focused Information — Use the listed reference numbers and compatibility guidance together with your engine's exact service information.
- Customer Support — Contact support if you need help comparing the gasket with your original part before ordering.
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