After the IMO (International maritime organization) announced GHG (green-house-gas) reduction plans, marine engine makers were confronted with serious challenges on their future business. According to the Plan, every ship in operation in the sea must reduce its GHG emissions by 50%. Thus, a radical fuel transition would be inevitable from residual oils into gas fuels, which will eventually mean hydrogen or ammonia rather than other low carbon fuel. Between the zero carbon fuels, ammonia is in the spotlight as a candidate to abate GHG emission from ships. However, burning ammonia still emits both unburned ammonia and nitric oxides in the real tail pipe and this can raise another emission issue. In this study, many low flashpoint fuels such as LPG, CNG, and hydrogen in addition to ammonia were investigated to draw a feasible option for the low GHG emissions from the internal combustion engine. As a result, ammonia was easily supplied into the diesel engine and it substituted some diesel so that the amount of carbon dioxide emissions were reduced from the test engine without any significant increase of NOx emission. Not only ammonia but also different low flash fuel mixes showed better combustion characteristics to reduce engine emissions than just the ammonia-diesel example.