I dont have a hole in the stern from the outboard? I am confused. There is the Grady drive bracket back there, but no hole. Did the older 228s have the motor snugged up like the 226 with a motor well and so forth? At some point in history the bracket was introduced, so I guess I answered my own question.
My borther's first boat was a SC brand called Renken and it had the OMC stern drive and that clearly had hole where the I/O unit came through the stern to mate with the motor ... is this the same general motor with an I/O unit? If not, then I am confused and I apologize. Then again, getting parts to keep her running may be an issue given OMC is long gone and the stern/sea drive is no longer made as others have clearly pointed out.
Ultimately, you know the boat and the condition of her. It is your call and if you go for it, enjoy her. Keep us posted on the choice.