A fluid flow diverter is provided in a standard rectangular header of a keel cooler for optimizing the coolant flow towards both the interior tubes and also towards the exterior tubes of the keel cooler. The upper and the lower covers are provided along their peripheral edges with a recess and a flange, respectively, that engage with each other when the upper cover is closed onto the lower cover. In various embodiments, the user interface includes an input area, a viewing area and a window area in one or more pages, where the input area is contiguous to the viewing area in at least one page.