Good comments. There was a big difference between the low-pressure military installations and the civilian-derived high-pressure conversions. The latter were built by a variety
of companies to different patents. Some worked much better than others. One of the installations I've been trying to find more info on was the pair installed in the Arkansas. Read's memoirs state that they were built by a firm in Memphis that was located on Adams Street. Someone with a commercial index of that city for the period might be able to identify the manufacturer. These engines were quite strong, and due to the size of the vessel, I suspect high-pressure. There is no mention of a condensor, even though the vessel was intended to be seaworthy. I've never seen definitive numbers on her displacement, but believe she was in the 800-900 ton range. This gives a basis for estimating her power. There were large river packets with similar or larger displacement on the Mississippi, so a riverboat machinery company should have been capable of building strong enough engines. The installations would have been complex, with gearing to the drive shafts. Low pressure installations had larger diameter cylinders and lower rotational speeds. Riverboats had a "doctor" engine to drive pumps, winches and the anchor capstan. Most ran off a line from the main steam line through a shut-off valve. I doubt that they used a separate small boiler to drive these systems on the basis of cost and safety. There is reason to believe that some of the vessels expecting orders to move kept a low fire in a single boiler. Hot coals from one could be shoveled into the others for a quicker ignition.