The Shammy Pilothouse model is the most sought after. Some originally came with a "Pisces" diesel which was less than 100 HP. I believe made by Chrysler. Most had 302 Fords. Some gassers have been repowered with 4108 Perkins or other slow turners that make them basically tugs.
I know many here think Shamrocks are junk. But this is a great set up. Just wonder what she turns up and how fast she is.