In most features the "Sargo"s were a repeat of the "Salmon"s, except for the return to full diesel-electric drive for the last four boats and the adoption of the improved "Sargo" battery design. The first six "Sargo"s were driven by a composite direct-drive and diesel-electric plant (two engines in each mode) in the same manner as the "Salmon"s. In this arrangement, two main engines in the forward engine room drove generators. In the after engine room, two side-by-side engines were clutched to reduction gears which sat forward of the engines, with vibration-isolating hydraulic clutches. Two high-speed electric motors, driven by the generating engines or batteries, were also connected to each reduction gear. The Bureau of Steam Engineering (BuEng) and the General Board desired a full diesel-electric plant, but there were some dissenting opinions, notably Admiral Thomas C. Hart, the only experienced submariner on the General Board, who pointed out that a full diesel-electric system could be disabled by flooding. Technical problems went against the use of two large direct-drive diesels in place of the four-engine composite plant. No engine of suitable power to reach the desired 21-knot speed existed in the US, and the current vibration-isolating hydraulic clutches were not capable of transmitting enough power. It was also not practical to gear two engines to each shaft. So a full diesel-electric plant was adopted for the last four "Sargo"s, and remained standard for all subsequent conventionally-powered US submarines.