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Designed Marine Hydrostatic Prop Drive

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Existing mechanical prop drive systems have the following limitations:

  • Mechanical drive systems are inherently inefficient.
  • Engine placement is fixed.
  • High knots require high engine RPM.
  • Low speed docking maneuvers are accomplished with plugging (bumping) the mechanical transmission in and out.
  • Finding the “sweet spot” where engine torque, RPM and fuel economy coincide is nearly impossible.


  • An engine was selected and an operating RPM was identified by the correlation of the torque, RPM, fuel efficiency curves.
  • The engine was given two operating RPM’s. A docking (low) RPM and an Operating (high) RPM. Prop speed was varied by controlling the hydrostatic drive.


  • Fuel Efficiencies Increased
    • Hydrostatic drives are 10-15% more efficient than mechanical drives.
    • By operating the engine at a constant RPM, the engine mass does not have to be accelerated.
    • By operating an engine at a constant RPM the exhaust is able to be tuned and engine performance is significantly increased.
  • Engine Noise Reduced
    • By operating an engine at a constant RPM the exhaust is able to be tuned producing significantly quieter operation.
  • Engine Placement is Infinite and Dynamically Variable
    • Effective use of limited space is now available.
    • Balancing non symmetrical loading is possible.
    • Dynamic movement of the engine is possible during operation allowing maneuvering assistance and variation of wetted surface area.
  • Docking Control Dramatically Improved
    • Hydrostatic drives are able to deliver power and speed in a smooth infinitely variable operation.