Roscoe, thank you ... I'll go with the 1978 reference. I picked up another 8HP Mariner which has the Serial Number:
Mariner 8M / 677 S 041322
I used your reference source and could you confirm that this motor is a 1981? I am hoping to utilize some of the parts from the 1978 to use on the 1981. Once again, thank you for your input.