That’s a great question and in theory makes sense . You’ll never get perfect synergy with rotation of blades matching water flow . You’ll always get a degree of what we call slippage or loss of thrust with prop driven craft , especially displacement hulls . A displacement hull is for example a ship or Shrimp Trawler that displaces a large volume of water with its hull laying deep in the water like if you push a 5 gallon bucket into the water without water flowing over the lip it’s displacing 5 gallons of water in that space . Then you have planing hulls like your speed boats etc that sit almost on top of the water at speed displacing very little volume in that space .
If the props get too much slippage you’ll then get the blades drawing oxygen from the water creating air bubbles around the blades and inefficiency creating violent shaking of the vessel ( cavitation ) where you think the boat is about to shake apart lol .
It’s a nasty kind of feeling but sometimes it’s unavoidable . You’ll see acceptable levels of cavitation when you look at the wash coming out the back of a boat and it’s a milky foamy colour . That’s the air being drawn from the water around the prop blades and spat out the stern with the thrust .
I hope that kind of makes sense . It’s sometimes all jumbledeboo to most if your not living it daily .
Also our Props spin on like a worm drive meaning they rotate 360 degrees directing thrust in any direction so we don’t have rudders .
View attachment 162365
So each of those props with nozzle surrounding rotate 360 degrees .
You can form angle combinations to create complex water flows that’ll make the tug go sideways in the water . They’re an absolute gem to drive .
Not sure if anyone has seen the Moran company tugs in the states zipping around but they’re the same .
View attachment 162368
So in each hand is a corresponding control lever that both rotates the props you see and a throttle to vary power delivery . No big steering wheel lol
