Dunno. Counter rotating props on modern boats is relatively recent. You can get twin out boards that go opposite. I know on inboard engines with direct drive, you have to have counter rotating engines. You can get the crate marine motors from Ford (or GM) spinning either way. A gear reduction transmission makes it go the other way, so I suppose a tranny could make the prop spin the other way.

My guess is on a military boat you wanted everything to be identical for interchangeability. They might have had some sort of trim tabs to balance the torque, I have an inboard and the engine torque affects the level of the boat more than the steering. On mine the rudder is right behind the prop, if it is not behind the prop or if you have multiple rudders, it might not be a big deal.

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