All internal combustion engines need fuel, air, and compression to run. For those looking for increased power you need to add one of the three. An easy way to do this and the way most diesel engine manufactures do is to add a turbocharger. Recycled exhaust air pushes a turbine wheel in the housing which on the other end forces air from the intake back through the cylinders with pressure we call charged air or boost pressure, this allows more fuel to be burned and creates more power. When the compressed air leaves the turbo it heats up and needs to be cooled down to increase the density so more air can be shoved into the cylinder. This is where the aftercooler comes into play. Raw water from the sea strainer is directed through a series of tubes and as the air flows through the fins surrounding to the tubes it cools down similar to a radiator in your car. Over a period of time these fins become plugged up with soot and other mineral deposits. If neglected air will be restricted from flowing through the aftercooler resulting in a loss of power, excessive black smoke, and a fuel sheen covering the water. The worst case scenario is the core begins to leak which will put sea water straight into the cylinders. This can all be easily avoided by keeping up with maintenance and cleaning the aftercooler every other year or 2000 hours.