From The Civil War at Sea, by Craig L. Symonds (Praeger, 2009), Kindle Locs. 78-97:
Despite their self-evident logistical limitations, the tactical superiority of paddle steamers in the Mexican War led Congress in 1847 to approve three new side-wheel steamers (the Susquehanna, the Powhatan, and the Saranac), and one with a screw propeller (the San Jacinto), all of which would play prominent roles in the Civil War. Like all steamers of that era, each of these ships carried a full suite of masts and spars and were labeled “auxiliary steamers” because they were expected to navigate under sail at least as often as they did under steam. They were, in fact, transitional vessels that straddled the age of sail and the age of steam. The principal reason for including the San Jacinto in the program was to compare a screw-driven vessel against a paddle-wheel vessel, a comparison that was marred by the fact that the San Jacinto had a number of engineering flaws-including a propeller shaft that was 20 inches off the centerlines.
Despite that, it very soon became evident that the side-wheel steamers were inferior to screw steamers. When the Susquehanna was dispatched to the Far East by way of Capetown and the Indian Ocean in 1851, it took eight months to steam 18,500 miles, and it burned 2,500 tons of coal en route. Simple division shows that this yielded an average of 7.4 miles of forward progress for each ton of coal burned. Because coal cost an average of about $10 a ton in 1851, it cost the government about $1.35 (more than a full day’s pay) for every mile that passed under the Susquehanna‘s keel. Moreover, the lengthy transit time was a product not only of its relatively slow speed (8-10 knots) but also of the fact that the Susquehanna had to stop eight times en route to refuel, spending 54 days in port recoaling. Finally, all of those coaling stops were necessarily at foreign ports because the United States had no overseas bases in the mid-19th century. Even after the Susquehanna arrived-finally-on station at Hong Kong, it remained dependent on foreign sources of fuel to stay there. Obviously, for a navy with far-flung responsibilities and no overseas coaling bases, steam power continued to have significant limitations.
A second problem with side-wheel steamers like the Susquehanna was that those enormous paddle wheels on each side obscured much of the ships’ broadsides, thus limiting the number of guns they could carry, and those big paddle wheels made very inviting targets. If one of the paddle wheels was damaged by enemy fire, the ship’s mobility would be dramatically affected, and the helmsman would need great skill to prevent the ship from yawing off course or even steaming in a circle. Navy Lieutenant W. W. Hunter suggested that the solution was to turn the paddle wheels on their sides and place them below the water line, thus putting them out of the line of fire and restoring storing an uninterrupted broadside. Dubbed the Hunter’s Wheel, this seemed to offer a technological and tactical solution. But in practice the Hunter’s Wheel proved stunningly inefficient. In 1842 the USS Union was engineered to operate with Hunter’s Wheels, but while they dramatically churned up the water and burned extravagant amounts of coal, the ship made no better than five knots, and in 1848 its engines were removed and it was employed as a receiving ship. In the end, the best solution proved, after all, to be Ericsson’s screw propeller, and in the mid 1850s, during a burst of naval expansion, the U.S. Navy returned to it for a new generation of warships.
The Powhatan and Susquehanna were among the “black ships” in Commodore Perry’s expeditions to Japan.