The topic comes up frequently on the proper method of installing our props. We have even heard of people loosing brand new ones because they weren't installed properly. We are also seeing new CNC machined props come through with recommendations to lap the prop to the shaft. This I feel is due to the machined finish on the tapered bore rather than a reamed finish. Since I had my X55 hanging in the shop, I thought I'd take a few pictures and go through the steps.
Keep in mind that our props are held on by a close fitting taper. According to one of the prop manufacturers, 70% of the torque is said to be transmitted through this fit and the rest is the key/keyway. I personally feel it's 100% because the taper fit shouldn't slip at all. I've seen some pretty sloppy keys with 0 evidence that any force has been applied to them.
Lightly clean the shaft with some emery paper or a Scotch brite pad: (If you don't have a new prop, clean the bore of it too)
Here's what you'll need. High spot blue (Prussian blue) and valve grinding compound:
Put a light coating of the blue on the shaft taper area:
Put the prop on the shaft and rotate back and forth in a small arc. Remove the prop and take a look at the blue:
You'll notice any high spots as lighter areas of the blue. This shaft, I made myself in the lathe about 20 years ago when I put a new bottom on the boat. The prop hasn't been off since then. (I know where all the rocks are on my lakes!!!) The prop is the original (64) to the boat. The taper fit isn't that bad considering it wasn't ever lapped in.
Spread some valve grinding compound on the shaft:
Put the prop on the shaft and with forward pressure on the prop, start turning it back and forth and rotating in 60 degree increments. When the compound seems to smooth out (no grit) pull the prop back and then forward again to get the compound re distributed. Rotate again. Repeat several times until there isn't much "grit" left to the compound.
Blue again and put the prop back on to check the lapping. High spots removed:
If not, repeat the lapping again.
Your shaft and the bore of the prop should have a real nice and even mat finish on it.
Clean all the compound and blue off with some solvent.
Fit the prop to the shaft without the key and mark the forward position of the hub with some tape:
The tape is a indicator that when you put the prop on with the key that it's forward against the shaft's taper. A common problem is that if the key is cocked or not in it's proper place, the prop will bottom out on the key rather than the taper.
If you are using a new key, it may need to be fitted. If too wide, drag it across a flat file:
Now, if you can't tighten the castle nut up to the point of getting the cotter pin into the hole, you can actually back off the nut to the hole. Tightening the nut has seated the prop on the taper and remember it's the taper that holds the prop on. It's the reason a puller is needed to break them loose. Anyone who is able to remove a prop with a hammer and a block of wood has a problem!!
BTW, every once in awhile, someone asks "why can't I grease or Never-Seize the taper so my prop will come off easier!! Well, you now know why and the correct answer is to tell them to get a decent puller!
Did you notice only my right cuff shows up in the thread. I was real careful after you've given me such a hard time!!!