The humble impeller, one of the smallest pieces of equipment on a boat, often causes the most problems. “More boating holidays and summer cruises are ruined by a failed impeller than by any other cause,” says John Wilson, a marine engineer who specialises in marine impellers at Westhaven-based General Marine Services.

“An impeller is one of the smallest parts on a boat but it is also one of the most vital and can fail at any time, usually without notice. It can also do substantial damage to other pieces of equipment; in some cases, totally incapacitating the engine.”

Wilson says that, while impellers are a key component of all pumps (found in marine engines, toilet systems, refrigeration and air conditioning units and wash down pumps), it is the impellers in the engine’s water pumps that are the most vital.

“If one of these fails, it not only stops the engine, it can also cause serious damage. Pieces of the broken impeller can end up in the heat exchanger or cause blockages in other parts of the engine. This can require major parts of the engine to be stripped down so these blockages can be cleared and the rest of the engine can be checked for small fragments of the failed impeller.

“This is not easy to do in a remote anchorage and the boat often has to be towed to back to port before the repairs can be completed.”

A failed toilet pump impeller, while not quite so catastrohpic, can also be very be unpleasant and take the gloss of an otherwise enjoyable holiday.

“Impellers can fail for a number of reasons,” says Wilson. “They are hard working parts and can simply wear out. They can also be damaged if they are run dry or if they have sat too long without running. We also see situtaions where the wrong impeller has been fitted, worked for a while and then failed.”

It is easy to spot the difference between a healthy and failed impeller. Boaties should always carry spare impellers and an impeller puller on board.

impeller damage 1

Wilson says impellers should be checked annually, either by an expert or by a competent DIY-er. Things to look for are cracks in the impeller’s blades, perished blade peaks, missing blades, missing blade parts and deformed blades.

“If boat owners are in any doubt, they should take the suspect impeller into an experienced marine engineer and get them to have a look at it.”

Wilson says the team at General Marine Services have seen so many impeller-caused problems, they have now established a special Marine Impeller Centre in their Pakenham St West showroom.

“We joke that the humble impeller is actually ‘Boating Enemy No 1’ because of the number of problems failed impellers cause each summer,” he says. “Of course, for the boaties affected, it is no laughing matter.”

He says GMS has worked hard recently to ensure they keep a wide and comprehensive range of impellers in stock, so that they can quickly provide a replacement. “We also make sure all our staff are well trained and experienced in recommending the right impeller, checking impellers for damage and properly replacing impellers if needed.”

impeller damage 3

Wilson says at this time of year he pleads with boaties to either check their impellers before setting sail or to take spare impellers with them.

“Impellers are relatively inexpensive and they are usually quite easy to replace. There really is no reason to put that summer cruise at risk; all it takes is a little preparation and an annual impeller check.”

The Humble Impeller

Found in: Engine water pumps, toilet systems, refrigeration and air conditioning units, wash down pumps.
Can fail: without notice.
Possible damage: stopped engine, damage to heat exchanger, blocked toilets, pumps that don’t work.
Solution: carry spare impellers on board at all times, carry impeller puller, check key impellers annually.