Sierra Drain/Fill Plug Washer for OMC Sterndrive & Cobra – 42489 – Pack of 5
Free returns on all eligible orders
You have 30 days to request a return. All sale items are final sale.
A proper seal at the gear lube drain and fill ports is essential for protecting your lower unit. This Sierra sealing washer is designed to crush slightly when the drain or fill plug is torqued down, creating a leak-free metal-to-metal seal that prevents gear lube from weeping past the plug threads.
Sold in a pack of 5 — enough for multiple service intervals or to keep a supply on hand for the season. Replaces OEM part number 311598.
Fits
- OMC Sterndrive
- OMC Cobra
- Johnson outboards
- Evinrude outboards
Key Features
- Replaces OEM part 311598 — direct-fit replacement
- Designed for use with drain screw 18-2387
- Crush-style sealing washer for a reliable, leak-free fit
- Pack of 5 — ideal for stocking up across a season
- Sierra marine-grade quality for freshwater and saltwater use
Best Use Cases
Replace this washer every time you change the gear lube in your lower unit — reusing a previously crushed washer is the most common cause of gear lube leaks at the drain plug. This pack is well suited for boat owners who service their own engines, as well as marine technicians servicing multiple OMC-powered vessels in a season.
Compatible & Related Products
- Mercury 4-Stroke Outboard Oil Drain Screw Washer – 12-803516
- Yamaha Drain Plug Gasket – 90430-08003-00
Parts Desk Insights
This is a high-turnover consumable — it should be replaced at every gear lube change, not just when it looks worn. A crushed or deformed washer will not re-seal reliably, and a slow gear lube leak in a lower unit can go unnoticed until significant damage is done. The 5-pack format makes it easy to keep a few on hand without overstocking. If you’re servicing an OMC Cobra or Sterndrive, confirm the drain screw part number (18-2387) is also in good condition before reassembly. OEM cross-reference: 311598. SKU: 47-42489.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.