Hi,
what are the main difference of SD50 and SD60?
Christian!
The most significant difference is hidden inside the long hood, a 645 engine block in the SD50 and the 710 in the SD60. I suspect the electrical system was also improved. The GP50/SD50 was not one of EMD's best models. A number of roads retired or sold them off while still running much older and more reliable GP40/SD40-2 models.
John
The short answer would be: 300 hp. The SD50 is 3500 hp and the SD60 is 3800 hp.
The Contemporary Diesel Spotter's Guide by Louis A. Marre states (p. 83) that "...the SD60, nearly indistinguishable externally from the SD50". Roster information on the particular railroads would likely be the best way to tell them apart.
Bill