The British engines are a pretty interesting subject. They were rated at 60 hp by one standard, but the indicated hp would have fallen in the 180-240 hp range. In the 1870's a number over virtually new units were available do to the rapid deterioration of many of the Crimean boats. They were built of green timber. Sounds familiar, doesn't it? In any case, the Brits came up with a new class of gunboats using two of these engines, the original shafts and screws coupled with a condenser and they performed very well. Some of that class lasted into the early 1900's. I have a list of when many of the defective vessels were retired and there literally must have been dozens of complete drive-lines available, engine, boilers, shafts, props and thrust blocks. All in mid 1863. They would have been available at surplus prices and in small lots. I've suspected for years that Maury had the Crimean class gunboats in mind when he proposed his own gunboat class. He already knew how much ordnance could be mounted on a vessel of that displacement. The Clown class only drew 4 ft of water and was intended for inshore work. Florida and Texas come to mind. Those engines could also have been the core for torpedo boats. The downside was that they were horizontal trunk engines and you needed mechanics who knew their business.