These engines were drawn from a plan found on line and were scaled for use with my HO Saw Mill. They are vertical engines of a kind more comonly found in marine applications but as small local sawmills were often built with used or repurposed equipment I thought it would be just right for my mill. Not as drawn on the plan however, with only one cylinder, so I drew it up with two units back to back, with a linkage so that both sides could be controlled with a single lever. Both versions are included here.
The bore and stroke of the engines are both 10". The levers are stop at center and control speed forward one way and speed in reverse the other. I think they would turn at about 230 RPM. I have no idea what the horsepower would be.
The distance from the floor to the top of the levers is about 6'-0" so your engineer will need a platform to stand on.