Cooling water pumps

First clarify pump type and engine compatibility

Before purchasing a raw water pump, you should know the engine manufacturer, model, and year of manufacture – many pump housings and impellers are manufactured for specific models and are not interchangeable. There are also design differences between the raw water and freshwater circuits that you must consider when making your selection.

Material and operating conditions

In saltwater operation, pump housings made of brass or bronze have a clear advantage over aluminum because they withstand saltwater better over time. The impeller itself is usually made of neoprene or NBR rubber – it should never run dry, as it will be damaged within seconds. Therefore, always put a spare impeller in your toolbox when laying up for winter.

When to change, when to replace completely?

The impeller is a wear part and should be replaced regularly depending on operating hours and manufacturer recommendations – regardless of whether it still appears intact externally. The pump housing itself has a significantly longer lifespan, but should be checked for scoring, corrosion, and leaky shaft seals. If damage is found there, a complete pump replacement is more sensible than a repair at sea.

After removal: Check direction of rotation and vane position

When installing a new impeller, pay close attention to the correct direction of rotation and the pre-tensioning of the vanes – an incorrectly installed impeller will perform less efficiently and wear out faster. A little petroleum jelly or special impeller paste makes insertion easier and protects against initial dry running for a few seconds.