With both thumbs pointing toward the bow of the boat, I have to grasp the drive shaft with both hands and curl my fingers in both directions the shaft can rotate. When my thumbs point forward - the fingers of one hand will curl over the top of the drive shaft and the fingers of the other hand will curl under the drive shaft. Whichever direction the drive shaft would have to rotate in order to propel the boat forward, the hand that agrees with that direction is the type of propeller.
Another option is to stand at the back of the boat looking toward the bow under the swim platform (preferably on the trailer!). Carefully rotate the propeller so that one of the blades is in the 12 o'clock (straight up -vertical) position. Whichever side of the propeller is closer to the bow, that's the type of propeller it is. For example, once you're in position and have the propeller oriented as described in this paragraph, the right side of the propeller being closest to the bow makes it a Right Hand propeller. If the left side of the propeller is closest to the bow, then it is a Left Hand propeller.
If this still doesn't make sense, try the U-tube video:
http://www.youtube.com/watch?v=Qa1Y1vPop00They call the propeller an impeller. Technically, they all pump material behind it which propels the propeller forward.
