During the conceptual and preliminary ship design stages, designers must ensure that the selected principal dimensions and parameters are good enough to deliver a stable ship (statically and dynamically), besides deadweight and speed. To support this, the initial intact stability of the proposed ship must be calculated, and for that, the lightship weight and its detailed breakdown are necessary to be known. After hull (steel) weight, machinery weight, mainly marine diesel propulsion and power generation machinery, plays a vital role in the lightship weight estimate of a ship directly. It also affects the deadweight, displacement, draft, and trim, which finally influence stability. The correct estimation of respective weights improves calculating a ship’s initial stability, typically designed and built. Hence, it would be advantageous for the ship designer to convince the shipowner. Weight control is not easy, especially since its consequences in terms of deadweight and stability could be disastrous. It should start right at the beginning and control throughout the design and construction phases. Marine diesel main engines (MEs) and auxiliary engines (AEs) of various power output (generators output for AEs), engine speed, and cylinder number of different engine manufacturers are collected. These are analyzed and presented in tabular and graphical forms to demonstrate the possible relationship between propulsion engine weight and power generation engine weight, and their respective power, speed, and power–speed ratio. In this article, the authors have attempted to investigate the appraisal behavior of ME weight and AE weight regarding engine power, generator power, engine speed, and power–speed ratio (independent variables). Further attempts have been made to identify those independent variables that influence the weight of the propulsion engine and power generation engine (dependent variables) and their interrelationships. A mathematical model has thus been developed and proposed, as a guiding tool, for the designer to estimate the weight of main and AEs more accurately during the conceptual and preliminary design stages.

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