Yes. Absolutely use a torque wrench for proper prop nut torque specs! Never use an impact wrench! Here is why. Before the advent of rubber prop hubs the propshaft and lower unit driveshaft were protected with a prop shear pin to insure the shear pin would break before causing damage to the drive shafts if hitting something with the prop. Then, due to larger horsepower outboards and advanced prop technology, prop manufacturers developed an expandable hard rubber hub inside the props to accomplish the same shock protection for the prop and drive shafts.
The rubber hub, when torqued correctly, will expand and and not only keep the prop from spinning inside the hub but also allow it to "give" and absorb shock if the prop hits an hard underwater object. The expandable hub works much like an old style rubber drain plug in a boat where you tighten it to expand so it doesn't come out.
Not every prop manufacturer uses the same density rubber so it's very advisable to use the recommended torque specified by the particular prop manufacturer because........ Too tight can not only crack or damage the rubber hub.....but can also prevent it from absorbing shock or giving a little if you hit a hard underwater object......causing prop shaft or drive shaft damage. Consequently, Not tight enough can cause you to spin the hub under load….ruining the hub. So there is a reason the prop engineers specify a torque range for their specific propellers. I can't tell you how many customers over the years that have prop issues due to improper torque on their props....either from being over torqued or under torqued.
Best way to tighten is to place a block of 2x4 between one of the prop blades and the bottom of the cavitation plate. This gives you a solid way of holding the prop stationary as you apply the torque.
It is a good idea to always apply a good coating of anti-seize on the prop shaft splines when replacing or re installing a prop.
Also it is imperative that you use the proper thrust washer behind the prop specific to the brand prop you use. All thrust washers are not the same. Using the wrong thrust washer can damage your prop shaft and/or your prop.
Get you a dedicated 1/2" drive deep socket. Usually it will be an 1-1/8" or 1-1/16" for V-6 or greater outboards and a torque wrench. Keep them in your tool bag in the boat so you will always have them.
ETA. It's also a very good idea to pull your prop off at least once a season to make sure you don't have fishing line wrapped around your prop shaft. The line can damage the shaft seal allowing water to get into your lower unit lubricant.
TAMU Wildlife & Fisheries Sciences
"Boat Racing is like a beautiful woman.... expensive, high maintenance....... but well worth the fun!"
