Marine Propulsion in the 1860s. - Boilers - Steam engines are external combustion engines, the fire is outside the engines themselves, inside a boiler. Most riverboats burned wood to make steam while most ocean and coastal steamboats burned coal. The Civil War also saw the first US Navy trials of fuel oil on a few boats. A marine engine description needs to specify the boiler type to know just how the steam was made. Boilers were described by their shape and pressure, high or low. There were two broad categories based on whether the water passed through the fire, called a water tube boiler, or vice versa, called a fire tube boiler. Beyond that, there were variations in the overall shape of the boiler, "ordinary," and "Scotch" being fire tube types, and "Western Rivers," and "Haystack" being water-tube types. There were many variations on the proportions and shape, a thorough explanation would bore you greatly, so I'll leave it there for now.
Engines - Nearly all engines used pistons that produced linear motion, which needed to be converted to rotary motion to turn a propeller. The way they did that is generally how they were named. The simplest had the piston cylinder horizontal working a piston shaft pointed at the center of a crank on the propeller shaft. To make that work, a second shaft (the connecting rod, or Pittman) connected the piston shaft to the crank. That was called a "simple, direct-acting" engine. If the cylinder pointed up at the propeller shaft it was a "vertical, direct-acting" engine. If the cylinder was above the shaft it was an "inverted direct-acting" engine. If the piston was angled up at the crank it was an "inclined, direct-acting" engine. If the cylinder was sitting on the keel vertically and operated a sidewheel shaft above, it could use a type of return connecting rod held rigid by a heavy four-sided frame that looked like a church steeple sticking out the vessel top. That was logically called a "steeple" engine. If the vertical cylinder was in front of or behind the sidewheel, and connected by the connecting rod to the sidewheel crankshaft and an intermediate rocking link it was called a "rocking beam," or sometimes "vertical beam" engine. There were also variations to save space, 1) where the connecting rod did not point forward, it pointed back at the cylinder (a return-connecting rod); or 2) operated inside a smaller cylinder taking up the middle of the piston (a trunk) engine. At this point take a Google break and look up pictures with these names because that really helps to figure this stuff out.
Engine steam valves - To automate the operation of the steam cylinders engineers designed a bunch of mechanisms that turned the steam on or off. Those were steam valves. There were lots of types, and their descriptions get way complicated fast. If you really want we can go there, later.
Condensers - Steam takes energy from wood, coal, or oil, to convert from water. Most steam machinery included a contraption called a condenser to save fuel by saving steam after it was used once. Without a condenser the steam was just blown up an exhaust pipe – then the engine was called a high-pressure engine. There were two types of condenser; jet and surface condensers. Jet condensers sprayed a stream of water inside a box to cool the steam back to water before returning it to the boiler. Surface condensers used cool water in pipes from outside the ship to cool the water. Condensers were important for efficiency, but were complicated and could get gummed up by the engine lubricants that got picked up in the water and steam. The most common lubricant was tallow and it could build up inside boilers, coating surfaces so they did not transfer heat well. They could also “foam,” making water gauges unreliable and therefore dangerous (inadequate water could make a boiler explode.)
Propellers – Steam machinery converted fuel into rotary motion, but had to transfer that into movement. All the machines that did that were called “propellers,” no matter how they worked, so paddle wheels, whether sternwheels or sidewheels, were still “propellers.” Paddle wheels could be simple fixed flat boards around the circumference of a cylindrical framework, or elaborate “patent” wheels with paddle boards that pivoted so that they stayed vertical, perpendicular to the water surface. Andy Hall showed the patent wheels of the blockade runner Cornubia/Lady Davis in a digital model earlier. Subsequent to paddlewheel propulsion, screw propellers were invented and have come to dominate ocean travel. Screw propeller design advanced quickly through the 1850s but the general shape of them was established in the 1850s. They had 2 to five blades that had curved surfaces of increasing twist and outlines either triangular or petal-shaped. They were described by their patent shape, diameter, and amount of twist. Most screw propellers were fixed and had to be dragged if under sail, but many could be uncoupled from the propeller shaft at the “cheese” (shaped) coupling and allowed to free-wheel. A few ocean-going steamers such as CSS Alabama could both uncouple the screw, but also lift it clear of the water in a patent lifting frame in a well near the stern.