Achieving greater levels of asset availability is the goal of many industries in diverse segments. This ambition is accompanied by actions aimed at increasing the reliability of these assets. Therefore, aiming at an operational campaign exempt from unexpected stoppages, one of the paths of success adopted by maintenance managers is the improvement of the equipment maintenance plan. This paper presents a strategy for developing a maintenance policy with a focus on reliability. Through multi-criteria decision-making methods (MCDMs), Entropy combination method and Multi-Attribute Utility Theory (MAUT) approaches, weights of criteria are established and classification of alternatives are performed in order to determine the critical components of a Kaplan hydropower unit, whose maintenance policy is used as a case study. The maintenance activities of these key assets are analyzed and improved under the opinion of specialists. This research obtained a ranking of the ten most critical items for the hydropower turbine and enabled the improvement of robustness the maintenance plan. The maintenance policy developed aims to improve preventive maintenance and predictive monitoring plan of the hydro generator to support an increase in availability and quality in the supply of electrical energy to society.