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Sierra 18-2642 Lower Unit Gearcase Seal Kit for Mercury/Mariner 200-300 HP Outboards

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

18-2642
08/02/2036 11:55 AM
Sale Price

$40.97

In Stock (9)

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Usually delivered within 2 days

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No Hassle Returns

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Live-in-stock inventory

Fitment guaranteed

Fitment guaranteed

Product Details

The Sierra 18-2642 is a lower unit gearcase seal kit engineered as a direct replacement for Mercury and Mariner outboard motors. It directly replaces Mercury OEM part number 26-816575A5 and is cross-referenced with GLM 87513 and Mallory 9-74209, making it a trusted aftermarket solution for high-horsepower V6 3.0L gearcase service.

This kit is designed for use on Mercury and Mariner 200–300 HP 3.0L Carbureted and EFI outboard engines. It contains all the seals, O-rings, and gaskets necessary to perform a complete lower unit gearcase rebuild, helping restore proper gear oil retention and preventing water intrusion into the lower unit.

Key Features:

  • Direct replacement for Mercury OEM part 26-816575A5
  • Includes all seals, O-rings, and gaskets required for a complete lower unit overhaul
  • Designed for Mercury and Mariner V6 3.0L Carb and EFI high-horsepower outboards (200–300 HP)
  • Cross-references: GLM 87513, Mallory 9-74209
  • Manufactured by Sierra International, a leading supplier of marine aftermarket parts
  • Helps prevent gear lube leaks and water intrusion into the gearcase

Sierra International is a trusted name in marine aftermarket components. The 18-2642 seal kit is built to meet or exceed OEM specifications, ensuring a reliable, long-lasting gearcase rebuild for your Mercury or Mariner outboard.

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