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Sierra 18-9803 Spanner Nut Wrench for MerCruiser Stern Drives

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

18-9803
06/02/2036 7:52 AM
Sale Price

$115.79

In Stock (7)

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Usually delivered within 2 days

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FREE SHIPPING

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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 18-9803 Spanner Nut Wrench is a specialized marine tool designed for removing and installing the driveshaft bearing retainer on MerCruiser stern drive units. This essential tool works with MC-1, R-MR, Blackhawk, all Bravo series, and all Alpha series drive units.

Key Features:

  • Direct replacement for Mercury Marine part number 91-17256
  • Compatible with multiple MerCruiser drive unit families including Alpha, Bravo, MC-1, R-MR, and Blackhawk
  • Precision-designed for proper fit on driveshaft bearing retainer nuts
  • Essential tool for stern drive service and lower unit maintenance
  • Durable construction for professional marine technician use

This spanner wrench is a must-have tool for anyone performing lower unit service, driveshaft seal replacement, or bearing maintenance on MerCruiser stern drives. The tool provides the proper leverage and fit needed to safely remove and install the bearing retainer without damage to components.

So far so good, great price.

Simple

Fast and easy

Google took me to your website. They had my hard to find part. Easy to use. Checkout was a snap. If this part is the 1 then this may be my new one and only parts store. LOWEST PRICES!

Very quick ordering with Amazon

It was quick and easy and matched my part to make sure it would fit. Just waiting to see how quick shipping will be now.

ORDER PROCESS WAS EASY, HOPEFULLY PART WILL ARRIVE OVERNIGHT AS IT WAS PAID FOR.

Ok so far

Good price and details. Product reviews were related to the site and not the product.

Fast and easy

Best prices I've found. Trust me I've looked!

I hope this works

Autoplicity had the best price on the Wiseco pistons I needed anywhere. Took a little longer to arrive than I expected but apparently that was due to the pistons being shipped directly from the factory. Otherwise a very good experience overall.

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