I (very respectfully) disagree with the comment about only the key fitting properly. You should view it as a two step operation. First without the key lap in the prop and/or set washers so that the last bit is as snug as possible. The danger about having any space between the back of the prop and the shoulder on the shaft is that as the prop pushes it may swedge itself further up the shaft - actually walking up the shaft due to the XXX HP you are using to drive it up the shaft. One day you'll run the boat and notice the nut isn't tight - and good luck getting the prop off!!
You can go to www.mcmaster.com and they have stainless shims (high priced VERY thin washers) so that you can work tight tolerances to make sure the prop is set to the shoulder if the bore is a little undersize, key the thing as mentioned, and then nut it up.
You guys have it covered, but I'll say this for posterity....the most critical part is making sure the key fits both slots. To be properly fit, sometimes you have to grind the key with a stone on only one half lengthwise - in other words dont grind the whole flat edge if it fits in one and not the other. You run the key along the edge of the stone so it actually has a step in it so it fits perfect in both halves of the slot. Thats the real measure of how well it fits. Even if you tighten it down with the nut to the shoulder and you can't turn it because of the pressure of the swedge, guaranteed if there is slop in one of the keyways the prop will lash itself under acceleration and decel and act like a hammer-drill on the key and possible shear it.....in some used props you can actually see how the keyway has been hammered when it was not fit properly.
Sorry if this is all elementary to most......just trying to save somebody some hassle if they didn't know....
Very good point. As usual, I learned that the hard way and cracked the shaft a millionth of an inch right at the corner of the keyway end. Bingo, shelling out for a new shaft...
The prop must be snug, at both ends, and the key must be tight in both keyways.
I will check it out. My reason for thinking the bore was deaper on my old prop was because the old prop nut had about a 1/4 inch from the nut to the cotter pin. The new one was so close to the cotter pin it was hard getting cotter pin in.
Don't worry about the bore untill you measure how far the blades are under the boat compared to the old prop. Put the old prop on by hand with a blade straight up and measure from the most rear part of the tip to the end of the cav plate. Put the new prop on by hand and do the same. This is comparing one prop to another with the blade at the same location. If you like your ride, make sure you do this when changing props. You might have to add spacers or shorten the shaft. Most everyone worries about the gap differance between the prop and strut for the ride which means nothing.----PALHAL
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