Lower Unit Fill and Drain Plug Washer 2-Pack for Johnson/Evinrude, OMC Cobra and Volvo Penta Applications (OEM 311598)
Lower Unit Fill and Drain Plug Washer 2-Pack for Johnson/Evinrude, OMC Cobra and Volvo Penta Applications (OEM 311598) is backordered and will ship as soon as it is back in stock.
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Lower Unit Fill and Drain Plug Washer 2-Pack for Johnson/Evinrude, ...
Lower Unit Fill and Drain Plug Washer 2-Pack for Johnson/Evinrude, OMC Cobra and Volvo Penta Applications (OEM 311598) is backordered and will ship as soon as it is back in stock.
Product Details
This Lower Unit Fill and Drain Plug Washer 2-Pack is an aftermarket replacement gasket set for compatible lower-unit gearcase service. It is listed for Johnson/Evinrude outboard, OMC Cobra stern/out drive, and Volvo Penta stern/out drive applications.
The washers are associated with Johnson/Evinrude OEM reference 311598, also shown in the leading-zero format 0311598. Marine parts catalogs identify this reference as a gearcase fill and drain plug seal or gasket. Confirm the original part number and plug configuration before ordering.
- Two replacement washers included
- Used to seal compatible lower-unit fill and drain plug positions
- Suitable for routine gearcase lubricant service when the application is confirmed
- Aftermarket replacement; not an OEM-manufactured component
Part Number References
Use the following verified product reference when comparing your original part. Part-number references do not replace model-specific fitment verification.
| Reference Type | Part Number | Description |
|---|---|---|
| Johnson/Evinrude OEM reference | 311598 | Gearcase fill and drain plug seal or gasket |
| Johnson/Evinrude formatted reference | 0311598 | Leading-zero format of the same reference |
Application Information
The company catalog identifies this washer for the following application groups:
| Brand or Product Group | Application | Fitment Guidance |
|---|---|---|
| Evinrude / Johnson | Outboard lower-unit fill and drain plug service | Confirm OEM reference and engine model before installation |
| OMC Cobra | Stern drive or out-drive fill and drain plug service | Confirm the exact drive model and original washer |
| Volvo Penta | Stern drive or out-drive fill and drain plug service | Confirm the exact drive model and original washer |
Do not rely on horsepower, year, engine family, or brand name alone to confirm fitment. Model, serial-number range, gearcase type, and plug design can affect compatibility.
Technical Specifications
- Product Type
- Lower-unit fill and drain plug washer or gasket
- Package Quantity
- 2 washers
- Primary OEM Reference
- 311598
- Alternate OEM Format
- 0311598
- Application
- Compatible gearcase, stern-drive, or out-drive fill and drain plug sealing
- Product Status
- Aftermarket replacement
What's in the Box
- 2× Lower-unit fill and drain plug washers
Installation Notes
- Turn off the engine, secure the boat, and allow the lower unit or drive to cool before servicing.
- Confirm that the replacement washer matches the removed washer and the specified part reference.
- Place a suitable drain container beneath the gearcase or drive before removing the service plug.
- Remove the fill and drain plugs as directed by the engine or drive service manual, and allow the lubricant to drain completely.
- Clean the plug threads and sealing surfaces. Inspect the plugs and housing for damaged threads, corrosion, or abnormal wear.
- Install a new washer on each compatible plug being serviced. Ensure each washer sits flat and centered.
- Reinstall the plugs using the torque specification in the applicable service manual. Do not overtighten.
- Refill the gearcase or drive with the specified lubricant and quantity, then check both plug areas for leakage.
Maintenance and FAQ
How many washers are included?
This listing includes two washers. The quantity may be suitable for replacing the washers at two compatible fill and drain plug positions, but the exact number required depends on the serviced unit.
What does OEM reference 311598 identify?
Marine catalog records identify 311598, also shown as 0311598, as a gearcase fill and drain plug seal or gasket reference for applicable Johnson/Evinrude equipment.
Will one washer fit both the fill and drain plugs?
Use one washer only where the plug and service manual call for this type of seal. Confirm that both plug positions use the same washer before installing two units.
Should the old washer be reused?
Replacement washers are recommended during gearcase lubricant service because a used washer may have been compressed and may not seal reliably after removal.
What should I do if the plug still leaks?
Stop operation and inspect the washer seating area, plug threads, sealing face, and housing for damage or contamination. Use the applicable service manual for the correct torque and repair procedure.
Is this an OEM part?
No. This is an aftermarket replacement washer set referenced to OEM part number 311598.
Important Fitment Information
- Compare the original washer, plug, and OEM reference before purchase.
- Brand and application-group references are not a substitute for checking the exact engine or drive model.
- Do not install the washer if its size, shape, or sealing surface differs from the original part.
- Follow the applicable manufacturer service manual for lubricant type, filling procedure, and plug torque.
About Sea Sierra
- We supply aftermarket marine replacement parts for maintenance and repair applications.
- Product references are provided to help customers compare replacement parts with their original components.
- Careful part-number and application verification is recommended before installation.
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