Shoot, that’s just the old 2hp West Bend Elgin / Chrysler / Sea King, etc that has been around forever. There are no secret pins or anything, I’m assuming you have removed the nut #61 from behind the clip #47. Stud #46 is probably corroded and seized in the leg.
EDIT: Take back what I said. There is a circlip #26 around the drive shaft which means the drive shaft has to come down with the gearcase. Perhaps the splines at the upper end are rusted into the crankshaft splines ??
