Compressed air starting systems seem to be pretty much universal for submarines, as well as a lot of other marine applications. American boats used compressed air. I remember something about air starting being used in S-boats (the German ones, not the American subs) as well, with a comment that you had to be careful backing out of a slip because you could run out of compressed air if you had to reverse too many times. (Something about having to shut down the engines to reverse the screws, though that's always seemed a little odd -- I'm fairly sure German marine engineers knew what a clutch was.)

The preference for air may have something to do with the amount of effort needed to turn over a big marine diesel. You're dealing with a compression ratio two or three times higher than in a spark engine, and these are huge engines. One of the engines used in American boats was a 16-cylinder, 10,097 cubic inch (165 liter) monster. There were four of these in these boats, plus an 8 cylinder auxiliary engine. 500 psi air was used to start them. You'd need a massive starter motor -- the diesel in the average car is in the 3.5 to 5 liter range, and the starter pulls about 40 amps turning it over.

The same engines and generators are used in trains, which I believe also use compressed air starting systems. Without trying to dig out a lot of engineering details, I suspect it's simply easier to spin up a big diesel by putting air into the cylinders than it is to spin the shaft with an electric motor.

J.T. McDaniel