A long shaft engine offers one the opportunity to make a much shorter engine than using a short shaft engine.

Sounds funny?

You make a shorter hub with a clearance hole all the way through. You thread the end of the long shaft at the correct length for your prop nut. The prop nut holds it all together. The hub itself can be Locktited to the shaft.

With a short shaft engine, your hub must have enough threads to grip the crankshaft and in addition, have enough threads to hold the prop shaft. This makes for a longer hub.

Enjoy,

Jim