Abstract: A duplex turbine replacement unit to up-grade an obsolete or worn out quad turbine unit and thereby obtain enhanced power plant operational and output efficiencies, while at the same time providing a turbine profile and method of installation wherein the duplex turbine replacement unit hereof conveniently adapts to utilizing the existing draft tube discharge floor holes as originally provided for the replaced quad turbine unit draft tube discharges thereby eliminating the extensive and expensive civil engineering site modification and re-work that would otherwise be necessary with conventional commercially available up-grading replacement turbine units, in addition to also providing a turbine replacement unit having an internally housed and protected wicket gate adjustment mechanism which thereby substantially reduces the hazard of damage thereto by entrained debris in the turbine water.