As of tonight I am shopping for a used lower unit. My motor is a 1983 johnson 50 hp 2 cyl. I was thinking that a 40-70 hp lower unit from 1979-1989 would work as long as it had the same number of splines on the shaft as my old one. I am just trying to confirm that info. So my question is: what year and hp lower unit will fit a 1983 50 hp 2 cyl.