Water pump impeller

clbkab

When should the impeller be changed and what symptoms does a worn impeller demonstrate?

Britinusa

I have heard every couple of seasons it should be changed, I'm thinking you will be overheating somewhat, I'm changing mine out today.

LaRea

When the impeller fails, you'll overheat within a few minutes.  If the impeller has partially failed, you might notice the engine running hotter than normal.  Or there might be no symptoms at all, which is why most people replace impellers every other year.  

clbkab

Thanks for the quick responses!  I will be changing my impeller before the season starts!

Cableguy Greg

I would change it every other season. If you have a Bravo 3 drive, keep a spare one on board.

MarkB

Mercruiser book and most certified mechanics indicate a change every 3 years. You will likely see a temperature rise in the engine, which will be the warning. Unless it is a catastrophic failure, then the temp will rise dramatically.

Dream_Inn

It's one of those items that is best to change before failure. I've seen them fail, and pieces can get lodged in every hose in the engine.  I change mine every 2 years.  Easy to do and good preventive maintenance.

DanD2

 Don't take any chances, Easy and cheap enough to change every two years.

Capt Ron

It all depends on how many hours you put on your boat in a season... Usually 100 hours is the time and every three years is the advice, however, I only put around 25 to 30 hours on my boat a season and every three years I throw away perfect impellers because the work involved doesn't make checking them an easy task for Merc's. I like the way Volvo does theirs on the end of the crankshaft..

Dream_Inn

I tend to disagree Ron.  It is even harder on the impeller when it's not used.  A long winter will set an impeller really quick.  I always change my impellers in the March time frame and it is crazy how the impeller is all shriveled up from the winter.  On most used impellers, if you bend the vanes back (opposite of the way they were bent), one can usually see cracks just starting at the bottom of the vane.  I will also add that the very first boat I owned, bought it used 2 years old.  I went thru an engine not knowing any better to change the impeller.  For me it was an inexpensive lesson learned.  (then several years later my risers cause water ingestion, another lesson, and another engine...and another story)

Maybe I should start another topic, but I'll put the question out.  Probably for anyone that keeps their boats on a lift, have you ever watched your water pressure (I use vesselview to monitor) when you first start up the boat.  I've now noticed on several boats in my marina, including mine, that after putting the boat in the water and starting it, there is no real flow of water through the exhaust elbows.  It takes several minutes (basically until the engine gets to temp) before water flows.  The pump has water to it (I've checked) and it is not causing harm to the impeller (I've gotten good just over the last few weeks at pulling the pump apart) and seems like it is air-locked.  It's almost as if there is a thermostat regulating it.  I know on raw water cooled engines it is regulated a bit differently, but I'd have thought water just gets pumped straight thru both the heat exchanger and the exhaust immediately.  Thoughts?