ORIGINAL: RCKen
No, you don't need a torque wrench. But you do want to get it as tight as you can get it. Here's what I recommend. First off, if you have one of those 4-way combo wrenches that will also remove glow plugs get a good grip on it with your right and and throw it as far as you can!!!
Seriously, those are no good for tightening a prop. What you do need is a good box end wrench and a glove (a good rag will do as well). Use the glove to hold the prop while you tighten it down, this will keep the prop from cutting your hand. Don't worry about over tightening because the nut and shaft are steel and will be very difficult to damage. Pull the wrench just as tight as you can get it. If get it nice and tight now you won't have to worry about ever throwing a prop. It's been at least 6 years since I've thrown a prop.
Ken
I hear this a lot. I use one of those wrenches, and haven't yet lost a prop, but then I REALLY turn hard on the wrench, (See the rest to qualify this statement).
I was told by a guy watching me just this weekend he didnt tighten them that much. Then, I fired my starter to run the engine dry so I could go home and guess what happened?[:@] Prop nut spun off LOL!! Fortunately the engine DIDNT fire up, so it was just the starter torque spinning it off not the motor.
Getting a box wrench into my kit tonight. Im just glad Ive been lucky till now, and that I didnt lose the prop.