The Flying Scott, from my sometimes dubious source, is a three-cyl first sold in ’58 as a 60-hp, morphing into a 75-hp in ’61. Looking at some parts list, it doesn’t seem that the lower unit or any part thereof interchanges with the smaller motors. They did produce that motor, probably basically unchanged, until ’69, when McC spit the bit. So the lower unit off any 60-or 75-hp would most likely work.