The Hunley only had about seven horsepower

[Franklin]

The Hunley weighed (I think) about 40,000 lbs yet was able to maneuver effectively on about seven shaft horsepower (at the most), a fact that could be of interest to those interested in designing a small submarine.

[tom28571]

The Hunley weighed (I think) about 40,000 lbs yet was able to maneuver effectively on about seven shaft horsepower (at the most), a fact that could be of interest to those interested in designing a small submarine.

I think you are being very generous. The Hunley did not have anything like that much power. There were 8 men cranking on the single shaft. I don't know how much power they were able to maintain over a reasonable time but the total was likely no more than 2 hp.