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Sierra 18-3121 Water Pump Impeller Plate for OMC Sterndrive/Cobra - Replaces 911703

Manufacturer

Sierra

<p>For nearly six decades, Sierra has established itself as one of the marine industry's most trusted names in aftermarket engine and drive parts. Founded as a specialized marine parts manufacturer, Sierra has grown into a comprehensive supplier of replacement components, instrumentation, and accessories for both recreational and commercial boating applications. Operating from their 300,000-square-foot distribution center in Litchfield, Illinois, Sierra serves boat owners and marine technicians worldwide with an extensive catalog of parts engineered specifically for the harsh saltwater environment.</p><h3>Marine Engine Excellence</h3><p>Sierra's reputation was built on delivering precision-engineered internal engine components and drive system parts that meet or exceed OEM specifications. Their <a href="/7570-sierra-engine-gasket-set-5404">engine gasket sets</a> provide critical sealing solutions for inboard and outboard motors, while their <a href="/7570-sierra-engine-complete-assembly-15341">engine complete assemblies</a> offer comprehensive replacement options for major overhauls. Each component undergoes rigorous testing to ensure reliability in demanding marine conditions, from corrosion resistance to temperature cycling performance.</p><h3>Instrumentation and Monitoring Systems</h3><p>Accurate instrumentation is essential for boat operators to monitor engine health and prevent costly breakdowns on the water. Sierra's comprehensive line of <a href="/7570-sierra-gauges-200483">gauges</a> includes everything from fuel pressure and temperature indicators to voltmeters and trim gauges, all designed with marine-grade materials that withstand vibration, moisture, and UV exposure. Their <a href="/7570-sierra-tachometer-gauge-1488">tachometer gauges</a> deliver precise RPM readings critical for optimizing engine performance and fuel efficiency. Supporting these instruments, Sierra's <a href="/7570-sierra-gauge-resistor-47908">gauge resistors</a> ensure proper signal conditioning and accurate readings across various sensor types and engine configurations.</p><h3>Expanded Product Portfolio</h3><p>In 2022, Sierra significantly broadened its scope beyond traditional marine engine parts to encompass a wider range of boating accessories and even outdoor power equipment components. This strategic expansion brought established marine brands like Shields and Moeller under the Sierra umbrella, creating a one-stop resource for marine maintenance and replacement parts. The company now offers fuel systems, electrical components, battery charging solutions, and NMEA electronics alongside their traditional engine parts lineup.</p><h3>Quality Backed by Industry-Leading Warranties</h3><p>What sets Sierra apart in the crowded aftermarket marine parts market is their commitment to standing behind every component they manufacture. Their warranty coverage extends beyond simple part replacement—it includes shop labor, haul-out fees, towing charges, and related incidental costs should a warrantied part fail. This comprehensive protection reflects the company's confidence in their manufacturing processes and quality control standards. For boat owners facing repairs far from shore or mechanics working on customer vessels, this peace of mind is invaluable. Whether you're maintaining an outboard motor, rebuilding an inboard engine, or upgrading your boat's instrumentation, Sierra's decades of marine industry experience and commitment to quality make them a reliable choice for keeping your vessel running at peak performance.</p>

Part Number

18-3121
08/09/2036 9:38 AM
Sale Price

$16.87

1 left at this price

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Usually delivered within 2 days

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Fitment guaranteed

Product Details

The Sierra 18-3121 is a marine-grade water pump impeller plate designed as a direct replacement for OMC Sterndrive and Cobra stern drive cooling systems. Built to meet or exceed original equipment specifications, this wear plate is an essential component of the water pump assembly, providing a precision sealing surface for the impeller to maintain optimal coolant flow and protect your engine from overheating.

Key Features:

  • Durable, non-corrosive marine-grade construction for long service life in harsh saltwater and freshwater environments
  • Precision fit ensures proper impeller contact and maximum water pump efficiency
  • Direct OEM replacement — replaces OMC part number 911703 and GLM part number 12760
  • Designed for use in OMC Cobra sterndrive water pump assemblies (1986–1993)
  • Sold individually; one impeller plate per package

The Sierra 18-3121 impeller plate is commonly serviced as part of a complete water pump rebuild kit. Regular inspection and replacement of the impeller plate helps prevent premature impeller wear and ensures consistent coolant circulation throughout the engine cooling system.

Great prices! Had exactly what I was looking for, for $20 less than anywhere else even with the shipping cost added in.

So far so good.

i will let you know when i receive. i like the feel of the cream but do not care for the smell.

Easy transaction

I need this for tomorrow. Thanks!

Smooth transaction. Price listed when searching on Google was not the price listed on website.

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No hassle ordering and fast quality shipping at a reasonable price.

Very good

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