Originally Posted by klem
Since I didn't see it already asked, were you applying the correct tightening torque? Bolts that are undertorqued are much more likely to back off. The best way to do this is with a torque wrench. A properly torque bolt clamping a hard material (unfortunately bronze isn't as hard as would be good) will almost never back off. The other way for the bolt to back off is if the prop wasn't fully seated initially and it moves a bit, the preload on it will go down similar to if it is not properly torqued. Also, a bolt that is loose will be subject to fatigue.
Yes, this could certainly lead to fittings loosening up, but don't over tighten of course. The procedure I follow:
1. Coat prop shaft and inside of prop hub and cone with appropriate marine
2. Firmly seat the prop.
3. Put cone in place and tighten. There is a hole bored horizontally through the hub which you can insert a small bar to tension properly -- I use a large phillips head
4. Lube the hub bolt and tighten. I don't usually use a torque wrench but certainly a good idea.
I've removed the props on my boat several times over 10 years to service
the shaft seals
. To date, I have never lost
a prop or found one to be loose (I usually give them a quick check a few times a season), but now you guys have me a little paranoid !