Can’t find correct propshaft

[Plumpdragon 0]

I just bought my first boat, I was told it’s a 1985 ski centurion, the motor runs but it does not have a prop shaft and I cannot seem to find out what size it needs, I know almost nothing about boats and I’m from the dirtbike world, where finding the OEM parts you need is as easy as a few clicks. Please any info you can give to point me in the right direction would be appreciated.