yes, I have seen that the part#s are different. The problem I have is that I am not sure what lower unit I have. I looked up the number on the power head and it came up as a 73 but comparing shafts on ebay it looks like the one I have is a 74 so I am wondering if I might have a newer lower unit on it or if it has the wrong shaft in it? the shaft is worn very bad where the bearing runs on it causing so much slop that it leaks through the oil seal. I don't know if it is worn from use or because it is the wrong shaft? is there any way to identify the year of the lower unit to be sure?
I am pretty sure the shaft diameter is different. 1974 has a different bearing and impeller. 1973 shaft has an o-ring groove around the top splines, 1974 has the o-ring internal in the crankshaft. Not interchangeable.
It does look to have an o ring groove but no o ring the diameter is about 5/8" at one at the lower unit end and steps down to about 1/2" at the power head end the splines are 5/8" 14 spline at both ends. Does this sound like the 73 shaft?
