The M18 x 1.5 A2-70 Stainless Steel Nylock Lock Prop Nut from Buckshot Racing #77 is a widely compatible marine fastener designed for securing propellers on a range of mid-to-high horsepower outboard motors.
 
Manufactured from marine-grade A2-70 stainless steel, this nut offers strong resistance to corrosion and is suitable for both freshwater and saltwater applications. It includes a nylon insert that provides a self-locking feature, helping to prevent loosening due to engine vibration.
 
The nut has a thread size of M18 x 1.5, requires a 27mm wrench (1-1/16 inch Prop Wrench), and measures approximately 3/4" in height.
 
This prop nut is compatible with a wide range of modern Mercury, Honda, Suzuki, and Yamaha outboard motors, all of which use metric propeller shaft threads in higher HP ranges.
 
Mercury Marine began transitioning to metric prop nuts around the year 2000. Most models produced after this date with larger horsepower ratings use M18 x 1.5 threads, including all Mercury 115 Pro XS (3-cylinder, 1.5L) and larger outboard motors. However, Mercury propeller shaft threading can vary across model years and engine families, so checking manufacturer documentation is advised.
 
Honda Marine outboards have used metric hardware from the beginning of their production in the 1960s. The M18 x 1.5 prop nut fits Honda outboard motors rated at 75 horsepower and above. Compatible models include the BF75, BF90, BF115, BF130, BF135, BF150, BF200, BF225, and BF250. These engines are equipped with propeller shafts that match the M18 x 1.5 thread size, making this nut a standard replacement option.
 
Similarly, Suzuki Marine outboards with 40 horsepower and above are mostly use M18 x 1.5 threaded prop shafts. Compatible models include the DF40, DF50, DF60, DF70, DF90, DF115, DF140, DF150, DF175, DF200, DF225, DF250, and DF300. These motors are commonly used in both recreational and light commercial marine applications and consistently feature metric threading.
 
Yamaha outboards are also manufactured to metric standards and support the M18 x 1.5 thread on models with 90 horsepower and greater. This includes popular outboard models such as the F90, F115, F150, F175, F200, F225, F250, F300, VMAX SHO 200, VMAX SHO 225, and VMAX SHO 2250. 
 
Other compatible applications include select BRP model Johnson and Evinrude ETEC outboards rated at 150 horsepower and above. These engines, particularly later models produced in conjunction with global manufacturing standards, adopted metric threading in their drive systems.
 
Given the broad compatibility across brands and models, the M18 x 1.5 A2-70 stainless Nylock prop nut serves as a reliable and consistent replacement component.
 
Why Replace Your Prop Nut?
 
A worn-out prop nut can lead to serious performance and safety issues:
 
Excessive propeller vibration – May cause gear chipping or internal damage to the lower unit.
 
Risk of propeller loss – If the nut backs off completely, the propeller can detach.
 
Reduced efficiency and performance – Improper prop positioning negatively affects hydrodynamics.
 
To prevent these problems, always torque the prop nut to 55 ft-lbs and align a flat surface with a washer tab, then bend up one of the washer tabs to secure it.
 
Reusing a worn or deformed nylon insert lock nut is not recommended. Over time, the nylon insert loses its locking strength, increasing the risk of loosening.
 
According to FAA and industry best practices, a mil-spec nylon lock nut should not be reused if it can be turned by hand once the insert engages the threads. The same principle applies to marine and racing outboard applications—always replace worn prop nuts to maintain gearcase longevity, performance, and safety.
 
Includes one (1) M18 Stainless Prop Nut or Buy 3, Save $3
 
Contact Mike Hill at +1-714-697-1716 or email mike@buckshotracing77.com for technical support.