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Hello,

I don't know the first thing about how boats function. Here I have a description. I couldn't find all the terms so it might sound funny. Would you please read it and see if it makes sense and correct the mistakes? Thank you ina dvance.

Currently, next to a Z-leg and an axle-box there is a different drive. The blades of its lower propeller are under the trunk of the boat, and the rest of the propeller is above the surface at high speeds. If it is needed, the vertical angle of the propeller's slope/incline can be adjusted for sailing at slower speeds. By shifting the axle of the surface drive horizontally, the boat is steered into desired direction. This system was installed in Italian patrol boats in 1960.
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Instead of sailing, say cruising, since you're talking about using the engine, not the sails.

And I THINK (I'm not sure!) that you change the pitch of the propeller, not its slope. As I recall, at some speeds, some pitches are more efficient.

Behaps an avid boatsman will come along and set us all straight.
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Thank you Grammar Geek.
Well there is an innovation for propellers on boats, and especially for yachts where the motor is stopped and the blades of the propeller fold down to reduce drag as it goes through the water.

So in this example, I suspect this might be the case.

If so.... I would then substitute 'If it is needed'... for... 'If necessary'

and 'the vertical angle of the propeller's slope/incline can be adjusted for sailing at slower speeds....to..... 'the rake of the propeller blades can be adjusted for sailing at slower speeds'.