Sierra Spanner Nut 18-3751, Replaces Mercury Marine 79448, For V-6 Reverse Clutch

The Sierra 18-3751 Spanner Nut is a stainless steel locknut engineered for V-6 stern drive reverse clutch assemblies. It is machined to precisely thread onto the driveshaft and hold the reverse clutch components in correct alignment and preload during operation. As a direct replacement for Mercury Marine part 79448, it restores original fit and function when the factory nut is worn, corroded, or damaged during a clutch or bearing service.

Constructed from stainless steel for corrosion resistance in the marine environment, this spanner nut is a small but critical component in the reverse clutch stack, and using the correct part number ensures proper torque retention and clutch engagement. It is sold individually and is priced per package.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3751
• Product Name: Spanner Nut
• Material: Stainless steel
• Weight: 0.23 pounds
• UPC: 030999316509
• Application: V-6 reverse clutch
• OEM Cross Reference: Mercury Marine 79448

Fitment

• V-6

Replaces (OEM)

• 79448

Frequently Asked Questions

What does the Sierra 18-3751 Spanner Nut replace? The Sierra 18-3751 Spanner Nut is a direct replacement for Mercury Marine part number 79448.

What engine application is the 18-3751 spanner nut designed for? Sierra 18-3751 is designed for V-6 reverse clutch applications.

What material is the 18-3751 spanner nut made from? It is made from stainless steel, which resists corrosion in marine environments.

How much does the Sierra 18-3751 Spanner Nut weigh? This spanner nut weighs 0.23 pounds.

Is Sierra 18-3751 a genuine Sierra part or an aftermarket copy? 18-3751 is a genuine Sierra International part, sold under Sierra's own part number as a replacement for Mercury Marine 79448.

What is the UPC for the Sierra 18-3751 Spanner Nut? The UPC for the Sierra 18-3751 Spanner Nut is 030999316509.

How is the Sierra 18-3751 Spanner Nut sold? The 18-3751 Spanner Nut is priced and sold per package as an individual locknut.

What role does the spanner nut play in a reverse clutch assembly? In the V-6 reverse clutch assembly, the 18-3751 spanner nut threads onto the driveshaft to secure and preload the reverse clutch components.

Will the Mercury Marine 79448 nut work in place of Sierra 18-3751? Yes, Mercury Marine 79448 and Sierra 18-3751 are the same replacement part, so either part number will fit the same V-6 reverse clutch application.

Does the Sierra 18-3751 come with washers or other clutch hardware? No, 18-3751 is the spanner nut only; it does not include tab washers or other reverse clutch hardware.