Outboards are generally produced in three shaft lengths, 15” short, 20” long, and 25” extra long.
To determine which one is right for your boat, simply measure the transom height directly on center from the top where the motor sits, straight down to the bottom of the boat. Do not include any keels.
If your transom height is approximately close to any of the above measurements, that will be the shaft length you will need. It is very important to match your boat with the proper outboard shaft length.