Gear is a power transmitting element among the rotating shafts by means of progressive meeting of projections which is identified as teeth. The purpose of the gear is transmitting torque (power) among rotating shafts when the central distance between the shafts is comparatively less.The main aim of the paper is to Design and Analysis of a helical gear for marine applications, by using empirical formulas and Calculation, from the data to draw a 3D model helical gear by using Pro/Engineer Software and the Structural and Thermal Analysis done by the Simulation Software (ANSYS).Structural and thermal analysis is done using two materials Nickel Chromium Molybdenum Alloy Steel and Aluminum Alloy A360. Structural analysis and thermal analysis is done to conform to the Displacement, Von Mises Stress, and thermal properties related nodal temperature, thermal gradient and thermal flux.