ABSTRACT: The high speed vessels are primarily designed for short distances services as public transport of passengers and vehicles. The range of high speed, according to the Code of high-speed vessels begins at 20 knots, which depends on the cruise speed you desire for your vessel; you will have to use the most appropriate type of propellant. In general, in the past 20 years, they have been building high-speed vessels with speeds above 33 knots, which meant installing water jet propellants coupled to powerful engines and therefore of high consumption of fuel, increasing operating costs and causing increased air pollution. Although the prices of fuel have been reduced to half, due to the sharp fall in oil prices, the consumption of fuel and the air pollution remains high at these speeds and powers used, in addition to that the reduction of the time spent on each trip is not excessive, mainly in short routes that are less than an hour . This article is about adapting a ship of high-speed service, with a maximum speed in tests of 34 knots and to reduce its operating costs (fuel, maintenance, etc.) and make it economically viable; before the transformation, this vessel was operating with a service speed of 22 knots, and with a consumption per mile of 135 litters of MGO. The transformation process has consisted by: ? Replacement of the two original water jet with four shaft lines with fix pitch propeller. ? Replacement of the two original main engines (2 x 6500 kW = 13000 kW) by four engines (4 x 1380kW = 5.520 kW). ? Changing the underwater hull shape to fit the new propellers and maximize its efficiency. ? Relocation of auxiliary engines, to achieve the most efficient trim. ? Installation of two lateral propellers to improve maneuverability and shorten the total time of journey. After the reform and the return to service of the vessel with a service speed of over 22 knots, it has been verified that the consumption per mile is of 45 litters MGO, representing a reduction of 65% of consumption and even more reduction of emissions as the new engines comply with the latest regulations.

KEYWORDS: High Speed Craft (HSC), Ship Propulsion, Propulsion System, High Speed Catamaran, MARPOL Annex VI, Marine Gas Oil (MGO), Improving the Efficiency, Energy Efficiency Operational Index (EEOI)

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