LRM1003

Hi there. Does anyone know what difference there is between the series I, II & III of these boats? I heard Mustang were a bit hit and miss on which were good boats and which were lemons. Also if anyone knows which years to stay away from. The horsepower seems to vary greatly as well. Looking at the most economical option for a boat of this size and whether Volvo Penta or Mercruiser is a better option. Any help much appreciated.