This paper presents a method to design and enhance the performance of speed governors for aged Hydroelectric Power Plants (HEPP) utilizing limited number of online site tests. First, the mathematical model for the governor is generated using plant parameters. Afterwards, the aging and backlash effects are added to the model in order to match the simulation outputs with the site measurements. The feed forward and Ziegler-Nichols (ZN) methods are examined in order to mitigate the impact of backlash. Between these methods the former one is selected since it also provides island-mode stability. The updated speed governor is applied to Gezende HEPP governor and performance progress is observed. (C) 2015 Elsevier B.V. All rights reserved.