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Sierra 18-4457 Exhaust Flapper Valve 4 Inch with Stainless Steel Clamp

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

18-4457
06/01/2036 11:53 AM
Sale Price

$23.37

In Stock (10+)

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Usually delivered within 2 days

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No Hassle Returns

No Hassle Returns

Live-in-stock inventory

Live-in-stock inventory

Fitment guaranteed

Fitment guaranteed

Product Details

The Sierra 18-4457 is a 4-inch external exhaust flapper valve designed to protect marine engine exhaust systems from water intrusion. This essential component prevents water from flowing back into the exhaust system when the engine is not running, which could cause serious engine damage.

Key Features:

  • 4-inch diameter flapper valve for standard marine exhaust applications
  • EPDM (ethylene propylene diene monomer) rubber construction for superior heat and weather resistance
  • External mounting design for easy installation and maintenance
  • Includes stainless steel clamp for secure, corrosion-resistant attachment
  • Prevents backflow of water into the exhaust system
  • Designed for marine inboard and sterndrive applications

This exhaust protector valve is a direct replacement part that helps extend engine life by keeping water out of the exhaust manifold and engine block. The EPDM material resists deterioration from saltwater, heat, and UV exposure, making it ideal for demanding marine environments.

Products specifications

Replaces

Merc 12644A

Size

4"

quick easy cheap

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The site showed items in stock, I hope that was accurate

I am not sure yet, I have not installed the product.

Very quick response and would do business with them anytime I could again

Great

Good

This place is excellent. Very easy to use. My parts were shipped on time, and they kept me updated with multiple emails throughout the process. Would definitely buy from these guys again. A++

The process seemed pretty simple to me. Will definitely use again.

Very convenient!

I have had a very good experience with Autoplicity and will look for more parts here. I called Customer Service and they were very good and accurate with me. It was easy, they were very nice, immediate response, and great price.

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