Following the tankers in the Museum, the screws on all of them do turn. I'll set me a few up for torpedo testings, and take some shots at some in the boiler area, and see if the engine sound stops then... It should cease shortly after going under, or if the boilers blow, but the game doesn't do damaged props or rudders very well either...
Edit: OK, quick run-through of the Tankers in a Single Mission, and even with hits in the boiler room area, ship in two pieces, props and rudders blown off, fire everywhere, and you can still hear the sound of the engines going, sometimes for a good while. I even blew one of the props off of the Medium Tanker, hit just in front of the stern, and the other prop kept going, and they were able to navigate and avoid my next shot at them, like there was nothing wrong. By the same token, the next ship, with minimal damage from a hit in nearly the same location (Large Modern?), and it couldn't do a thing to avoid a steep-angled hit amidships. The Large Fleet Oiler was the toughest, in that I had the first two hits were duds, then they "combed" the next two shots, one to either side somehow, but I did finally get it... We'll look into the engine sound torpedobait, because with some of the ships, the sound does stop, either as they're sinking, or if the hit is in the boiler area. Co-incidence, or by-design, we'll try to find out.
