Turbocharger
A Turbocharger uses the energy in the exhaust gas of a diesel engine to drive a turbine, which spins a compressor on the same shaft that forces more air into the engine cylinders. Packing more air in lets more fuel be burned, so a turbocharged engine produces far more power than the same engine breathing naturally.
Nearly all modern marine main and auxiliary engines are turbocharged; large slow-speed engines may have several turbochargers. Turbocharger cleanliness and condition strongly affect fuel efficiency and reliability, so they are a regular item in the planned maintenance and performance monitoring of the engine.
The turbocharger is what makes a modern marine engine powerful and efficient for its size, so its condition directly affects both the power available and the fuel burned. A fouled or failing turbocharger shows up as lost power, higher consumption and exhaust problems — which is why performance data is watched closely.
Why are marine engines turbocharged?
To produce much more power from a given engine size by forcing extra air into the cylinders, allowing more fuel to be burned efficiently. It improves both power output and fuel economy.