SeaLux Marine Boat Propeller Nut Mercury 11-69578 Brass Nylock 3/4" · Propeller Nut Replaces: Mercury 11-69578 · Replaces: 35-70 hp Mercury Outboards · Finish/Coating: Plain · 3/4" Hex Nylon Insert lock nut · Thread Direction : Right Hand This is a 3/4" shaft, 10 TPI nylock nut How to find out this lock nut will works for you. Step 1: measure your shaft diameter, if 3/4", yes, Step 2: measure count on how many threads on 1 inch shaft, if 10 thread, yes, this will fit. or every 1/2 inch shaft has 5 complete thread cycle Worn or scored thrust washers and prop nuts can cause damage to your prop shaft and propeller face. Protect your drive system by changing your thrust washer and prop nut when replacing or inspecting your propeller. compatible with: • Mercury 11-69578 • Sierra 18-3704 • Mallory 9-73901 Threads are molded into the nylon insert locking the bolt into place. Nylon Insert Lock Nuts typically have a cased metal outside formed into a hex pattern easily torque by a wrench or socket. ASME B1.1 Class 2B thread requirement. The use of brass, however, is somewhat limited due to its softness; primarily used for appearance. Brass is commonly used by electrical and communications industries, builders hardware and some marine applications.