Ship alternatively running fuel gas main drive engine and fuel gas generator engine

A ship comprising:

• a liquefied natural gas (LNG) storage tank containing LNG;
• an injection engine designed to use only fuel oil for a first power operation and further configured to use both LNG and fuel oil for a second power operation;
• wherein the injection engine is configured to consume less power in the first power operation than in the second power operation;
• a generator designed to use LNG to generate electricity;
• a motor operable using the electricity generated from the generator;
• a propulsion mechanism configured to propel the ship with propelling power;
• and
• a clutch system configured to connect or disconnect between the injection engine and the propulsion mechanism and further configured to connect or disconnect between the motor and the propulsion mechanism,
• which enables the ship to operate in a first mode of propelling power and a second mode of propelling power,
• wherein when the ship is operating in the first mode of propelling power that is below a reference level, the clutch system is configured to connect the motor to the propulsion mechanism and disconnect the injection engine from the propulsion mechanism, whereby the propelling power comes only from the motor such that the propelling power is generated by the use of LNG only,
• wherein when the ship is operating in the second mode of propelling power that is above the reference level, the clutch is configured to connect the injection engine to the propulsion mechanism and disconnect the motor from the propulsion mechanism, whereby the propelling power comes from the injection engine such that the propelling a power is generated by the use both LNG and fuel oil.