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Sierra 18-70939 Mercruiser Exhaust Manifold Molded Hose - Thermostat Housing to Starboard

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

18-70939
08/06/2036 11:55 PM
Sale Price

$40.79

1 left at this price

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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 18-70939 is a high-quality replacement exhaust manifold molded hose designed to connect the thermostat housing to the starboard exhaust manifold on MerCruiser stern drive engines. Built to withstand the demanding conditions of the marine environment, this preformed hose ensures a precise, leak-free fit for reliable engine cooling system performance.

Key Features:

  • Direct replacement for the thermostat housing to starboard exhaust manifold connection
  • Precisely molded shape for a drop-in fit — no cutting or trimming required
  • Engineered to meet or exceed OEM specifications
  • Constructed from durable materials rated for the high-heat marine exhaust environment
  • Designed for MCM/MIE GM V-6 and V-8 engines (305 and 350 CID)

Sierra marine parts are manufactured to meet or exceed the original equipment specifications they replace. As a trusted supplier to OEM engine manufacturers and boat builders, Sierra delivers the quality and fitment you expect for your MerCruiser stern drive cooling system.

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One of the most reasonable prices I saw after looking at a number of different sites. This site also ja good reviews and shipped very quickly. Very happy with th purchase.

great ordering process. Just waiting for product to arrive.

This is definitely a great company I had questions about my order and it will prompt you get right back to me. I'm extremely pleased with the purchase that I have made through this company

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