When I was in the Navy in the early 70’s I was on board an old LKA which had 8 LCM 6’s. Four forward of the superstructure, and four aft of the superstructure. These landing craft weighed in at about 60 tons and were powered with GM671’s. They were twin screw and about 56 feet long and 14’ beam.
At the forward and aft decks, the 8 LCM-6s were off-loaded with 60 ton booms. And they were OLD style, all wire rope controlling. A bosun’s mate would direct each booms operators with hand signals.
We would pick up these 60 ton “Mike” boats and put them over the side. The boats were crewed by (I think) 4 people; a coxswain (who drove the craft), an engine man (responsible for the machinery) a bow hook, (handled the forward lines) and another crew member for various line handling and other duties as ordered by the Coxswain.
MARIN, please note, these boats regularly moved sideways by engines and throttles only! These guys were experts at boat handling. They would have to position them alongside the ship and stand by as cargo lifted over the side. Jeeps, six boys, palletized cargo, you name it, if it was needed it got loaded! It was an incredible dance to watch. And I remember that like yesterday!
So yes, I know a twin screw powerboat can be moved sideways solely with twin screws and rudders. Feel free to reply to me.