Sierra Prop Nut 18-3700, Brass, Replaces Mercury Marine 11-52707, Fits Force Outboard 120, 125 & 150 HP

The Sierra 18-3700 is a brass propeller nut engineered as a direct replacement for the original hardware on select Force outboard motors. It secures the propeller onto the propeller shaft, providing the clamping force needed to keep the prop seated correctly during operation. The nut is finished in white and machined from brass, a material chosen for its corrosion resistance in marine environments where saltwater and freshwater exposure quickly degrade lower-grade fasteners.

This part carries a 1/2 inch thread with Unified National Coarse (UNC) threading, a right-hand, fully-threaded design, and a hexagonal head for use with a standard socket or wrench. It is built to the same specification as the original equipment nut it replaces, so no modification is required for installation. The 18-3700 is commonly stocked alongside the 18-3200 and 18-3701 for technicians servicing a range of Force outboard horsepower classes and model years.

Fitment covers Force outboard motors rated 120, 125, and 150 horsepower across the specific model years and drive/model variants listed below. Always confirm your outboard's horsepower, year, and model letter against the fitment table before ordering to ensure correct fit.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3700
• Material: Brass
• Color: White
• Exterior Finish: Machined
• Thread Size: 1/2 inch
• Thread Type: Unified National Coarse (UNC)
• Thread Style: Right Hand
• Thread Coverage: Fully Threaded
• Screw Head Style: Hexagonal
• Item Dimensions: 4 x 1 x 5 inches
• Weight: 0.13 pounds
• UPC: 030999236944

Fitment

• Force outboard, 120 HP, 1991, All models
• Force outboard, 120 HP, L-Drive, 1990, All models
• Force outboard, 120 HP, L-Drive, 1991, models B, D
• Force outboard, 125 HP, L-Drive, 1989, All models
• Force outboard, 150 HP, 1989, All models
• Force outboard, 150 HP, 1990, model A
• Force outboard, 150 HP, 1990, models B, C, D
• Force outboard, 150 HP, 1991, All models

Replaces (OEM)

• Mercury Marine 11-52707
• Mercury Marine 11-52707Q1
• Pleasurecraft R017066
• Chrysler Force F7000
• Honda 90301-ZW1-003

Frequently Asked Questions

What does the Sierra 18-3700 prop nut fit? The Sierra 18-3700 fits Force outboard motors rated 120, 125, and 150 horsepower, across the specific model years and model-letter variants listed in the fitment table, including L-Drive versions of the 120 HP and 125 HP models.

Is the 18-3700 a direct OEM replacement? Yes, this brass prop nut is built to replace the original equipment nut on covered Force outboards without modification, matching the original thread size and fastening design.

What OEM part numbers does the 18-3700 cross-reference? The 18-3700 replaces Mercury Marine 11-52707 and 11-52707Q1, Pleasurecraft R017066, Chrysler Force F7000, and Honda 90301-ZW1-003.

What material is the prop nut made from? Brass, machined and finished in white, which resists corrosion in both saltwater and freshwater use.

What thread size does the 18-3700 use? It has a 1/2 inch Unified National Coarse (UNC) thread, right-hand, fully threaded, with a hexagonal head for a standard wrench or socket.

How much does the 18-3700 prop nut weigh? The Sierra 18-3700 weighs 0.13 pounds.

Does the 18-3700 fit my Force outboard if it's a different model letter? Fitment depends on the exact horsepower, year, and model letter of your Force outboard; the 18-3700 covers specific combinations such as 120 HP 1991 all models, 150 HP 1990 models B, C, D, and others listed in the fitment table, so confirm your motor's specs against that list.

What is the difference between the 18-3700 and the 18-3200 or 18-3701? 18-3200, 18-3700, and 18-3701 are separate Sierra part numbers that are often listed together for the same Force outboard applications, but 18-3700 is a distinct part number and must be matched to your motor's specific fitment row rather than substituted automatically.

What is included when I order the 18-3700? The order includes one Sierra 18-3700 brass propeller nut.

Is the Sierra 18-3700 genuine Sierra or aftermarket? The 18-3700 is a Sierra-brand part manufactured as a replacement for the original Force outboard hardware, sold under the Sierra part number 18-3700.

What color is the 18-3700 prop nut? It has a white finish over the machined brass body.