Changing an Impeller
Gas-engine raw-water pumps have small impellers that are easy to change with ordinary tools (shown below). The raw-water pump impellers on big diesels are typically threaded for an impeller puller—a simple tool that extracts the impeller. Lubricant helps impellers go back into pumps with ease. If an impeller fails, be sure to piece it back together by locating any missing chunks, typically at the heat exchanger inlet, or in open-cooled engines, in the thermostat housing.