“I was thinking more like 11 hp with a steam engine due to the much higher torque per hp that steam produces. Guess I was wrong maybe others will chime in.”

In fact there is no difference, a horsepower is a horsepower, be it steam, or an IC engine, or a horse!

Horsepower is the rate of doing work, and defined as 550 ft-pounds of work output per second, or 33,000 ft-pounds of work output per minute. Work is defined as a force applied through a distance.

This can be with a high speed engine with low torque, or a low speed engine with high torque, either way the power output is defined the same.

The relevant parameters defining engine horsepower is shaft torque (T), and rotational speed (RPM). The torque here is the average torque produced by the engine, not the maximum torque for design of the connecting rod and bearings, etc., which is often several times greater than the average torque.

If the torque produced by applying a force to a lever (attached to the shaft), say an applied tangential force of 1 pound, with a 1 foot long lever arm, the torque is one pound-foot. However the work done in one revolution of the shaft is actually a movement of 6.28 feet, (2 x Pi x Radius), so in one revolution this condition produces 6.28 ft-pounds work. The equation relating engine torque and RPM then is:

HP = RPM * Torque (pound-ft) * ( 2 Pi ) / 3,3000