Yes, modern subs count target rpms, or turn-count, of the screws.
"Con, sonar: Sierra 23 is classified as a "whatever" class freighter, making 75 turns on one four bladed screw."
"Sonar, con aye. Do we have an estimated speed on Sierra 23?
"Con, sonar aye. Estimated speed 13 knots based on turn-count."
"Sonar, Con aye."
Just an example of what I listened to every watch while underway. The above numbers are in no way accurate, by the way. Just used as an example.
All modern navies have accurate databases containing estimated ship speeds based on class, turncount, number of screws and number of blades per screw. Even if a ship has 2 screws, but is running on a single screw.
I do not know how extensive such a database may have been in 1939, if such existed.
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My U297 build thread
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