Has to be a prop shaft as driveshafts will not interchange on those 2 models.
It is drive shaft on the lower unit didn't change the gears from the 93 pinion gear forward and reverse gear are all the same I just change the drive shaft so now my drive shaft instead of being a 13 spline is now a 4 spline so now that lower unit will work on my 81 Evinrude. should I put that spacer in like on the evirude or should I leave it the way the Johnson had it
Oooooops.

Been there, done that, ....against all advice, just like this poster.
My result....and my prediction, is that the pinion gear will wear badly and break up in the near future and take out some or all of the other gearcase components.
Still....a good teaching moment...this is not a DIY unless you have the equipment....or the luck of the Irish.
Make sure you have Sea Tow on speed dial.
