Water Pump Base Gasket – Fits OMC Cobra Sterndrive 2.3L–4.3L (Replaces OMC 911698)
Water Pump Base Gasket – Fits OMC Cobra Sterndrive 2.3L–4.3L (Replaces OMC 911698) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Water Pump Base Gasket – Fits OMC Cobra Sterndrive 2.3L–4.3L (Repla...
Product Details
This Water Pump Base Gasket – Fits OMC Cobra Sterndrive 2.3L–4.3L (Replaces OMC 911698) serves as a crucial adapter, sealing the connection between the water pump base and the gear housing. It is specifically designed for OMC Cobra sterndrive engines within the 2.3L to 4.3L range, ensuring a precise fit and preventing leaks.
This gasket is a direct replacement for Sierra part number 18-0911 and OMC part numbers 911698 and 778112.
- Installs between the water pump base and the gear housing.
- Engineered from durable materials for a reliable, long-lasting seal.
- Designed to meet or exceed original equipment specifications for fit and function.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Sierra | 18-0911 |
| OMC | 911698 |
| OMC | 778112 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For OMC Cobra models, this gasket is compatible with the following sterndrive applications.
| Brand | Model | OEM Part No. | Notes |
|---|---|---|---|
| OMC | Cobra 2.3L | 911698 | For sterndrive applications |
| OMC | Cobra 3.0L | 911698 | For sterndrive applications |
| OMC | Cobra 4.3L | 911698 | For sterndrive applications |
Technical Specs
- Product Type
- Water Pump Base Gasket
- Installation
- Between water pump base and gear housing
- Housing Material
- Gasket material (specific type not documented)
- Dimensions
- 6.0 × 7.13 × 1.03 inches
- Weight
- 0.48 ounces (13.6 g)
What’s in the Box
- 1 x Water Pump Base Gasket (OMC 911698/778112)
Installation Notes
- Disconnect the battery and ensure the engine is cool.
- Drain the cooling system to prevent fluid loss.
- Carefully remove the water pump housing and the old base gasket.
- Thoroughly clean both mating surfaces, removing any old gasket material or sealant residue.
- Position the new gasket correctly on the gear housing.
- Reinstall the water pump base, ensuring it is aligned properly.
- Tighten the bolts to the manufacturer's specified torque in a crisscross pattern.
- Refill the cooling system, reconnect the battery, and start the engine.
- Check for any leaks around the gasket area and allow the engine to reach operating temperature.
Troubleshooting & FAQ
How do I know if this gasket fits my sterndrive?
This gasket is designed for OMC Cobra sterndrives from 2.3L to 4.3L. Verify your model is listed in the compatibility table and that the OEM part number (911698 or 778112) matches your service manual.
What are the signs of a failing water pump base gasket?
Common symptoms include visible water leaks around the pump and gear housing connection, engine overheating due to cooling system pressure loss, or water contamination in the gear lube.
Is any sealant required during installation?
Generally, this type of gasket is designed to be installed dry. However, always consult your engine's service manual. Some mechanics apply a very thin layer of non-hardening sealant as a precaution, but overtightening or excessive sealant can cause the gasket to fail.
How often should this gasket be replaced?
It is best practice to replace the water pump base gasket whenever you are servicing the water pump (e.g., replacing the impeller) or if the gear case is separated for any reason. Proactive replacement prevents future leaks.
Could a bad gasket cause my engine to overheat?
Yes. A leaking gasket can allow air to be sucked into the cooling system or water to escape, reducing pump efficiency and leading to poor circulation and overheating.
What’s the difference between OEM and this aftermarket part?
This listing is an aftermarket replacement, not an OEM component. It has been engineered to meet or exceed original equipment manufacturer specifications using comparable materials. Our parts are made in an ISO 9002 certified facility and are batch-inspected for quality and consistency.
How fast do you ship and what does it cost?
We ship worldwide quickly, with typical transit times of 5–15 days for most regions. Standard shipping is free. Expedited shipping options, where available, will be presented at checkout.
What is the warranty and return policy?
This product is covered by a 1-year warranty against manufacturing defects under normal marine use. If you encounter any issues, 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/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.
Payment & Security
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