[Sailor Steve]

Okay! Here's the rundown from Conway's All The World's Fighting Ships: 1906-1921 and 1922-1946:

'S' Class, Elco type (S-1, S-18 - S-41): BS diesels plus electric motors.

'S' Class, Lake type (S-2): BS diesels plus electric motors.

'S' Class, Navy Yard type (S-3 - S-17): NSLE, MAN or BS diesels plus electric motors.

'S' Class, 2nd group (S-42 - S-47): BS diesels plus electric motors.

Barracuda class: diesels plus electric motors.

Argonaut: diesels plus electric motors.

Narwhal class: diesels plus electric motors.

Dolphin: diesels plus electric motors.

Cachalot class: diesels plus electric motors.

Porpoise class: diesel-electric plus electric motors.

Shark class: diesel-electric plus electric motors.

Perch class: diesel-electric plus electric motors.

Salmon class: diesels (composite drive) plus electric motors.

Sargo class: diesels (composite drive) plus electric motors.

Seadragon class: diesel-electric plus electric motors.

Gato, Balao and Tench classes: diesel-electric plus electric motors.



So the Porpoise class were the first to have diesel-electric drives. The Salmon and Sargo classes reverted to direct-drive diesel because of rising fears of leaks disabling the electrical systems. The Seadragon group of the Sargo class went back to diesel-electric, and they stayed with that system afterwards.

Conway's isn't clear as to what is meant by (composite drive), so I can't explain that; I just copied it as they have it.

I also can't verify the information with another source, but the editor for the United States ships section was Norman Friedman, so it's almost certainly correct.

So there it is.