Prof. Emeritus Femenia presents an updated and modified coverage chapter that introduces the thermodynamics, combustion, heat transfer and heat engineering associated with marine power cycles and steam plant heat balances. This is based on a long career of teaching, consulting and research related to both marine and land-based power plants. Following a review of thermodynamic principles, the fundamentals of combustion and heat transfer are introduced. Ideal power cycles are presented including regenerative and reheat vapor cycles. The thermodynamics and heat transfer associated with marine boilers are then briefly presented. The external thermodynamics of marine steam turbines and the estimation of state lines are discussed. This sets the stage for the introduction to the thermodynamics and heat balances of marine regenerative and reheat steam plants. The chapter closes with a discussion of waste heat recovery and gas turbine and steam combined cycles. This chapter provides excellent text material for marine applied thermodynamics and heat engineering. It would also provide a valuable review for marine engineering PE license study.