Sierra 18-3719 Pinion Nut - Replaces 11-35921 - 5/8 Inch Hex Nut for Mercury Outboard Propeller Shafts

The Sierra 18-3719 Pinion Nut is a 5/8 inch hex pinion nut used on Mercury outboard propeller shaft assemblies. It is machined and built to meet or exceed the quality of the original equipment part it replaces, making it a reliable choice when servicing the lower gear housing or performing a pinion gear/shaft rebuild. The nut secures the pinion gear onto the driveshaft, and correct torque on this fastener is critical to proper gear mesh and backlash in the lower unit.

This pinion nut is commonly ordered alongside related lower gear housing hardware, such as seal kits, washers, and tab washers, when a technician is already inside the gearcase. Each Sierra 18-3719 is sold individually and is manufactured to original fitment and thread specifications so it installs and torques the same as the factory nut it replaces.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3719
• Size: 5/8 inch
• Fastener Type: Hex
• Exterior Finish: Machined
• Inside Thread Size: #8
• Compatible Groove Diameter: 0.63 inches
• Item Dimensions: 0.39 x 0.39 x 0.39 inches
• Weight: 0.03 pounds
• UPC: 030999875648

Fitment

Used on Mercury outboard propeller shaft / lower gear housing assemblies.

Replaces (OEM)

• 11-35921

Frequently Asked Questions

What does the Sierra 18-3719 pinion nut fit? The Sierra 18-3719 pinion nut is used on Mercury outboard propeller shaft and lower gear housing assemblies to secure the pinion gear onto the driveshaft.

What OEM part number does 18-3719 replace? This nut replaces OEM number 11-35921.

Is the 18-3719 nut the same size as the original equipment nut? Yes, it is a 5/8 inch hex pinion nut built to the same fitment and thread specifications as the OEM 11-35921 nut it replaces.

What is the pinion nut made of and how is it finished? The Sierra 18-3719 is a machined hex fastener with a machined exterior finish.

What are the dimensions of the 18-3719 pinion nut? It measures 0.39 x 0.39 x 0.39 inches and has a compatible groove diameter of 0.63 inches.

How much does the Sierra 18-3719 pinion nut weigh? This pinion nut weighs 0.03 pounds.

How many pinion nuts come in one package? One Sierra 18-3719 pinion nut is included per package.

Is Sierra 18-3719 genuine OEM or an aftermarket part? The 18-3719 is a Sierra-manufactured replacement part, built to meet or exceed the quality of the original equipment 11-35921 nut it replaces.

What other parts are typically replaced along with the pinion nut during a gear housing service? When installing a Sierra 18-3719 pinion nut, technicians often also replace the related lower gear housing seal kit, washer, and tab washer at the same time.

What thread size does the 18-3719 pinion nut use? The Sierra 18-3719 has an inside thread size of #8.