The water pump impeller of any outboard motor needs to be serviced on a regular basis, usually annually, this helps to maintain pump performance, function, cooling and power. However, most owners we deal with do it less often and can end up with greater issues.

It is a wise idea to keep a spare impeller on board just in case that your impeller fails — an impeller failure at the wrong time can be disastrous.

Flexible impeller pumps are common in shower drain sump pumps, some bilge pumps, wake board ballast pump systems, oil changing systems, Shower pump and lots of other applications.

HOW DO IMPELLERS BECOME DAMAGED?

Your boat’s impeller is a series of rubber impeller vanes moulded around a hub. The tips of these flexible vanes can wear out for a variety of reasons including simple use or if the boat is in sandy water. Abrasive sand like material can cause the impeller to wear out faster.

Impellers can also wear out by becoming stiff and brittle due to the motor sitting unused for several years or being exposed to heat. Water lubricates the impeller, and if it’s run dry, the impeller can be ruined in a few seconds.

WHAT HAPPENS IF THE IMPELLER FAILS?

If your impeller fails, the pump can’t pump cool water to the engine causing your engine to overheat. If you discover that your impeller is failing early on, you might avoid major problems. However, if you don’t change your impeller before it fails, the results can be catastrophic to your engine.

Why Impeller Pumps Fail

Flexible impeller pumps work best when run regularly. If your pump sits for months with the impeller in one position with the blades on one side bent, it may “take a set” and may blow a circuit breaker on startup (if it’s electrically driven). The impeller may also stick to the housing and come apart when the pump starts. Impellers are damaged by debris that get sucked in, by chemicals, and especially by running dry. All it takes is a plastic bag blocking the raw water inlet, or a sea cock left closed when you start your engine, and your impeller will soon be a shredded mess.

Of course, you should check the wet exhaust on your transom for the proper flow of cooling water each time you start the engine. You should check the impeller’s condition during your annual service and every 200 hours of operation. Correctly installed impellers may last for several years, but you should stick to a schedule of preventative instead of emergency maintenance. Just the same, an impeller will eventually fail while in operation, and usually at an inconvenient time. You should carry a spare onboard, since the impeller is one of the vital components of your engine’s cooling system.

Impellers Nitrile vs Neoprene vs Polyurethane

There are several different types. Neoprene impellers are used for engine cooling, fresh and salt water transfer. Neoprene is suitable only for pumps where small amounts of oil or diesel fuel are present.

Nitrile impellers are used for bilge pumps and the transfer of heavily contaminated water (oil or diesel).

Polyurethane impellers are used for ballast pumps on boats where reverse direction is required. They are design to withstand systematic abuse.