Here is my situation. My boat has SSM II drives on it now. The props are 15x23 3 blade cleavers. Labor day weekend I bent the ear of one of the props and Johnnys prop shop in Detroit says they cant fix it, it is too thin. From what I have been reading my props are a 19 spline small shaft similar to the shaft in a SSM III. Will 3 or 4 blade props off a SSM III fit on my drives? I believe they are both 19 spline and 1 3/8 dia shafts

They will fit the shaft but not fit the application. Most of those drives were mounted pretty deep and need that small diamter/thin prop. If you had the bigger props trimmed they would work. But I would not run a 4 blade as they are harder on the drive.

Honestly dude, I would yank the ssm ii's off, and bolt TRS on the boat. Get yourself some bravo/trs style 4 blades. The boat will probably run alot better.

Check ebay for some small shaft, small diameter cleavers for the ssm ii. Ive seen them on there quite a bit.

As intriguing as having the SSM IIs hanging off the back I know your right. I'm just now getting the boat back in the water after 7 years and getting back into using the boat. Im putting a lot on my money right now at replacing stuff that has deterorated over the years ( raw water hoses, bilge pumps, electrical parts) I'd sell the SSM IIs but dont know how much they are worth. Maybe I could pick up TRS lowers to bolt to my uppers.