ORIGINAL: Umi_Ryuzuki

Take your prop shaft to the hardware store.
Ask to see the K&S brass tubing.

Put the first tube that fits, over your propeller shaft.
Put the second tube that fits over the first tube, and the propeller shaft.
Put the third tube that gits over all second tube and over all three.

Buy a tubing cutter
You will need solder and a soldering iron also.

When you get home, take the three tubes off the shaft.

From the smallest tube cut two 1/8th inch long pieces off.
Clean the inside edge out with an X-acto knife till the two pieces slide smoothly over the propeller shaft.

Cut two 1/4 inch pieces off the next larger tube.
Again clean the inside edgest so that the little 1/8th inch long pieces of the smallest tube will slide in.

Cut the third and largest tube to a length that will run from the motor, out through the hull and to the propeller. This should somewhat shorter than your propeller shaft.

Solder the two small pieces of tube flush with the end of the largest tube.
When finished, that tube will then have a small bearing at each end, for minimum friction, and can hold grease inside to keep water from getting into the boat.