Abstract
The frequent cause of ships' detentions by port authorities are abnormalities of ship power plant functioning. Each extended ship lay time in port results in waste of ship operating time thus costs rise to shipowners. This is connected with improper ship power plant management. In order to avoid this, a ship engineer should have at his disposal computer aided system supporting him in managing of ship power plant. Such a system can be worked out on condition that mathematical formula which represents the decision - making process of an engineer has been built. The present work shows approache to the problem according to the situation in which the engineer is made to take certain decisions. In formulation of the most substantial operating states of a ship like lay time in harbour and sea voyage the ‘knapsack algorithm’ was applied. For both approaches objective function was formulated.