RE: Toro 25 prop hub
Looks to me like the thread on the crankshaft end is 8mmx1 and the prop bolt is 5/16-24. This set-up would be for electronic ignition as the flywheel is not used and the hub would screw on to the crankshaft. Of course the 8mm thread could be at the end of the shaft too. I make all my hubs to look like that but I do CH ignitions on all them. I just stripped a Toro 25 to start to convert so I have not measured the threads yet.