Sierra 18-3721-9 Stainless Steel Locknut 7/16" 5-Pack

The Sierra 18-3721-9 is a high-quality stainless steel locknut with a nylon insert designed for use with MerCruiser inner transom studs and propeller nuts for Mercury 39 and 60 engines (1968 and newer, 8 spline). Each Sierra product meets or exceeds the original equipment part it replaces, ensuring reliable performance in marine applications.

Key Specifications:

• Thread size: 7/16" - 20
• Material: Stainless steel with nylon insert
• Package quantity: 5 locknuts per package

OEM Cross-References:

This locknut is interchangeable with GLM 21170, Mallory 9-72004 and 9-72004-10, MerCruiser Stern Drive 11-21298, 11-22178, 11-24648, 11-29241, 11-33962, 11-34933, 11-82671015, and Mercury Marine 11-134391, 11-22178, 11-34933, 11-46355, 11-82671015, 11-859116, and 11-95702.

The stainless steel construction with nylon insert provides corrosion resistance and secure locking capability in harsh marine environments, making these locknuts ideal for propeller installations and transom assemblies on Mercury and MerCruiser engines.