Colonel John Stevens had watched the trials of Fitch's steamboat, and knew that he was watching a boat built on a shoestring by amateurs. He also realized that the principle was sound, and even if Fitch could not pull it off, a more polished and well funded venture could pull it off. In 1792 Stevens had a steamboat on the Hudson river, and several advancements followed. Steven's got his first patent on steam propulsion of boats in 1792. That is signicant because it was well before Fulton's steamboat, which is generally regared as the first successful steam powered ship.
In 1804, years before Fulton's boat, Stevens built a steam boat with two counterrotating screw propellers. This photo is of a replica of Steven's double screw boat, built in the 1860s. The second photo is a drawing of the engine, gearing, and propellers of the 1804 boat, which was refurbished years later and measured at 8 mph.