Shaft length

[s_strayer]

After you stop laughing, how do I determine the shaft length of my outboard? I have a 1973 Mercury 1150. I have pulled the power head off and am in the process of rebuilding. I'm finding some part number differences based on shaft length. What is the criteria for a short shaft? For a long shaft? Can you take measurements without pulling the shaft? Thanks

[boats.net]

The easiest way is to measure the transom of the boat it came off. If it is 20" then it is a long shaft, 25" Xtra Long, 15" Short.