The major diameter of the crankshaft output end is 0.474". The threaded section measures 0.310" peak to peak on the threads. With the thread gauge I have the threads lined up with the 25G blade reasonably well and even better with the 1.0. Since this set of gauges is marked as "metric and standard" I'm guessing the 25G was the standard and the 1.0 metric. My knowledge of threads is limited so I measured the length of the threaded portion at .590" and counted 15 threads over that length. This gives me 25.4237 TPI wich given a reasonable margin of error corresponds to my thread gauge measurements. I'm guessing this is a metric thread of M8 x 1. Somebody more knowledgable please feel free to comment.

Now I need to find somone who makes a prop hub to fit this application.