The study compared the performance of a marine Solid Oxide Fuel Cell (SOFC) power plant for several fuels. A thermodynamic analysis was performed for a methane, methanol, diesel, ammonia, and hydrogen-fuelled SOFC powerplant. The highest electrical efficiency was found for methane (58.1%), followed by diesel (57.6%) and ammonia (55.1%). The carbon fuels (methane, methanol, and diesel) resulted in relatively low heat efficiency and around 15% reduced power density. The highest total efficiency was found for the ammonia-fuelled SOFC system. The heat quality in the methanol, diesel, and hydrogen system is insufficient for heat regeneration for the saturated steam net of the ship.