The UK Ministry of Defence (MoD) operates a wide range of small, high performance boats, used in varying environments, and locations throughout the world. These boats primarily operate using outboard motors (OBMs) due to the optimum power to size and weight ratios they provide, and the ease of maintenance compared to inboard motor boats. The use of OBMs has, with the exception of a large and heavy 27hp diesel (compression ignition) OBM, necessitated the use of Petrol (CIVGAS - F67). This dependency evolved from the difficulty encountered developing a reliable compression ignition OBM over the full power range required (20–250hp) at acceptable power to weight/size ratios. Given the lack of a perceived market for such an engine, very little development work was done in this area in the private sector. The requirement to run OBMs on CIVGAS presents a number of problems for the MoD, including logistical, availability (especially for Special Forces), and safety (especially for HM Ships required to store the fuel on the upper decks). The Marine Propulsion Systems Integrated Project Team (MPS IPT) within MoD’s Defence Logistics Organisation (DLO), was therefore mandated to develop solutions aimed at removing MoD’s reliance on CIVGAS. This resulted in a two pronged approach investigating both micro-gas turbines and multi-fuel OBMs. This paper will present the issues encountered and the development work completed to-date developing multi-fuel reciprocating OBM technology. The primary focus has been developing direct injection, spark ignition multi-fuel OBM technology, capable of using petrol, AVTUR (F34), AVCAT (F44), diesel, and marine distillate oil (MDO - F76). The paper will discuss the project plan, the technologies involved, development work, including test and trials, and the way ahead for the future.

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