How often should Impellers be replaced

V

vv1212w

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Have twin 350 Mercruiser inboards and had the Impellers replaced in both engines 4 years ago when one failed. Going into the 4th season in Michigan fresh water. Is there a time frame to replace Impellers? Thanks
 
In fresh water, I would say every couple to three years. If possible, change them now. At 4 years, you are on borrowed time.
 
depends... but 4 years is beyond what most will recommend.

factors that will affect impeller life :
-frequent haul out and launches where it will run dry for a few seconds
-taking a set during winter
-running in shallow/silty water

i usually get 4 or 5 years out of mines... knock on wood :-)
 
My mechanic says every 3 years whether it needs it or not. My current boat was just months shy of 4 years and my impellor crapped out while IN the water. Now I'm on the 3 year plan with this boat too.
 
Are these the impellers that are in the fresh water pump, or the one in the Alpha drive?
 
since you winterize the boat I would pull them each fall to avoid a set then reinstall if they look good.
 
bfuss... raw water pump.. not the circulation pump which doens't have a rubber impeller. raw water pump on most engines (stern drive or inboads) is installed on the engine... only mercruiser, in a stroke of genius, went and buried a service item in the drive ! :-)
 
I do mine every 2 years which is 280-360 hours
 
not sure what you mean. the seawater pump with a rubber impeller is usually a bolt on addition to the engine. The circulation pump behind where the fan would be does not have a rubber impeller.
Yes that is another in a list of mercury unpleasantness.
 
pdecat, I was just wondering about your Mercury unpleasantness? I think you will find most marine engine applications are like you mention. Please tell me of who does this anyway different. Yes, there are some gear driven rubber impeller pumps on larger diesel engines, but most circulating pump are not the positive displacement type nor do they need to be, they are for circulating the coolant is the block and the rest of the cooling system.
 
We boat year round in fresh water. We run about 100hrs a year and replace the impeller every other year. I have done this on both an engine mounted pump and one in an Alpha outdrive. Seems to work, I have never had an impeller fail.
 
I am talking about the raw water pump down low very low in the bilge. I changed this last year took me all darn day to button it back up. So I am reading here that I "should" be good doing this every other year?
 
unpleasant ness:
Some very complex raw water cooling systems
Riser/manifold designed to kill the engine if it fails
Impeller in drive leg
ss bolts in aluminum castings near or in the water
Alluminum in salt water, period
oil filters and starters in impossible locations
plastic pulleys
exhaust shutter valves
no drain cocks on block

Im sure other will add to the list but IMO the #1 boat engine maker should do better.
 
- sloppy ignition wiring routing
- engine blocks painted black, so detecting oil leaks is nearly impossible
- I/O's that sound like a car accident when you shift into gear
- self-destructing mechanical fuel pumps
- Riser/manifold designed to kill the engine when it fails (that's not stolen from Bruce, I changed a word)

oops, this is starting to feel like a hijack...

- water pump design that makes changing impellers take twice as long as it should

I changed my port impeller last month. It was 4 years old. It some of the vanes were "set" after the winter, but there was no cracking and the blades rebounded considerably after being removed from the housing. I was on borrowed time, but every year seems excessive.
 
pdecat, I was refering to inboards, I/O's and the rest of the marine engines out there. We all know most of them are adapted for marine use. Sometimes they're easy to work on, but most of the time, no such luck. The engine builders and the boat builders seem like neither one cares about servicing the engine. I was talking one time to the CEO of a boat builder and bitched about a certain repair scenario. His comment was, we only build them we don't fix them! Even the high end stuff with big diesels can prove interesting. These days, have you looked under the hood on your car, now that's a nightmare.LOL
 
Now you all know the REASON they paint them black...
 
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