A fuel control system adapted for calculation of a fuel efficiency of a fuel and water mixture of a marine engine, the fuel control system comprising: a mixer ; a fuel source fluidly coupled to the mixer , the fuel source being configured to measure a flow of fuel to the mixer ; a water source fluidly coupled to the mixer , the water source being configured to measure a flow of water to the mixer ; a mixture flow meter fluidly coupled to the mixer , the mixture flow meter being configured to receive and measure properties of a fuel/water mixture from the mixer , the properties comprising a measured flow of the fuel/water mixture; and a controller communicatively coupled to the fuel source , the water source , and the mixture flow meter , characterized by said controller being configured to calculate the fuel efficiency based on the measured flow of the fuel, the measured flow of the water, and the measured flow of the fuel/water mixture, wherein the controller being configured to calculate the fuel efficiency based on the measured flow of the fuel, the measured flow of the water, and the measured flow of the fuel/water mixture comprises the controller being configured to calculate the fuel efficiency based on equation: SFOC = α K ∗ Be ∗ Q TEST Q CONT − EDP , where: SFOC = specific fuel oil consumption (g/kWh); Q TEST = net calorific content of the fuel during test (MJ/kg); Q CONT = net calorific value of the fuel oil during the engine's baseline characterization (MJ/kg), which may be referred to as factory acceptance test; α = power adjustment factor; K = ratio of indicated power; Be = fuel oil consumption on test bed (g/kWh); and EDP = Engine driven pumps (g/kWh). a mixer ; a fuel source fluidly coupled to the mixer , the fuel source being configured to measure a flow of fuel to the mixer ; a water source fluidly coupled to the mixer , the water source being configured to measure a flow of water to the mixer ; a mixture flow meter fluidly coupled to the mixer , the mixture flow meter being configured to receive and measure properties of a fuel/water mixture from the mixer , the properties comprising a measured flow of the fuel/water mixture; and a controller communicatively coupled to the fuel source , the water source , and the mixture flow meter , characterized by said controller being configured to calculate the fuel efficiency based on the measured flow of the fuel, the measured flow of the water, and the measured flow of the fuel/water mixture, wherein the controller being configured to calculate the fuel efficiency based on the measured flow of the fuel, the measured flow of the water, and the measured flow of the fuel/water mixture comprises the controller being configured to calculate the fuel efficiency based on equation: SFOC = α K ∗ Be ∗ Q TEST Q CONT − EDP , SFOC = specific fuel oil consumption (g/kWh); Q TEST = net calorific content of the fuel during test (MJ/kg); Q CONT = net calorific value of the fuel oil during the engine's baseline characterization (MJ/kg), which may be referred to as factory acceptance test; α = power adjustment factor; K = ratio of indicated power; Be = fuel oil consumption on test bed (g/kWh); and EDP = Engine driven pumps (g/kWh). <EOS>