Impeller question: how often?

[Pub911]

How often should you replace your raw water pump impeller?

I know the havoc it can cause if it breaks up. Fortunately my every 2 year replacement regimen has kept me from that fate. But is there a rule of thumb?

FYI, my engine is a 1993 Universal/Westerbeke M4-30 and I put about 100 hours on it every season in New England. If it matters in the reply, I typically use potable purple or pink antifreeze to winterize the boat, so the impeller is awash in that stuff all winter.

[hellosailor]

Well, rubber part makers generally say they should be replaced every five years or sooner. Most boat folks would say to do it annually as part of annual maintenance because you can be sure it will still be good after just one year. And if it fails and a fin breaks off--that can go downstream and clog something, so better to do it too soon and just waste money. (!)

The quality of the rubber, the effect of the antifreeze...who knows. There was a company making higher price higher quality silicon impellers, don't know if they are still around but that might be worth looking into. All "rubber" isn't the same.

[sailingdog]

I would recommend that every two years be a minimum for replacing the impeller. It depends....if you end up running the impeller dry for a bit, then make the replacement sooner...since that is likely to cause it to heat up, become brittle, and more likely to fail.

[gulftex]

I replace my impeller every two years.I also have a unaversal engine I have installed a screen in the water line betwen the pump and the heat exchanger,catching broken parts of impeller.

[BarryL]

Hi,

I don't have a scheduled replacement time. I check it in the spring and if it looks Ok I leave it alone. It is very easy for me to access the impeller, and i have spares, so changing it at any time is not difficult.

BTW, last spring I removed the impeller and inspected it. I saw the vanes were cracked at the root. I replaced with a new one. In July I had reduced flow from the exhaust. I removed the pump cover to find that on my 3 month old impeller, 2 vanes were missing and 2 more were cracked. The next impeller I installed was a Globe, made of different material.

Since it seems (to me anyway) that a new impeller is just as likely to fail as an older one, I don't see the benefit of changing every year (or every other year).

Lastly, I usually put about 50 hours on the diesel each year.

Barry

[kwaltersmi]

I just picked up an impeller kit on eBay and plan to add this to my annual list since the parts are inexpensive. You could also follow SD's 2 year minimum recommendation with a check of the current impeller's condition at haulout.

[lancelot9898]

Originally Posted by BarryL

Since it seems (to me anyway) that a new impeller is just as likely to fail as an older one, I don't see the benefit of changing every year (or every other year).

I agree especially now that many items are coming from China. During the winter months my impeller is sitting in antifreeze and I think that may prolong its life. I used to change the thing every two years or so until one year after about 3 months of use the new one failed. This was due to using a grease that was not compatible with the material in the impeller so I now use a dish water solution to lube the new impeller at start up.

[Maine Sail]

Originally Posted by BarryL

The next impeller I installed was a Globe, made of different material.


Barry

Barry,

I too tried the Globe impellers but found them very problematic. below are some quote and photos from another forum. My failures were the center hub spinning free of the blue impeller. This was a tough one to trouble shoot as it looked fine. The next one the tolerances were off ever so slightly and she would not "prime".


Images courtesy P. Shed

Originally Posted by P. Shed

I was removing the sea water impeller from a M25 this morning . I do it each fall after haul out. To my surprise the impeller was cracked on every vane. This impeller was new this spring. The one I took out was a rubber type and was still like new but was old so changed it out . This is a # 815 . I would say there are only 35 hours on this impeller.


I will be taking it back tomorrow. Also going back to rubber type (black)

Sorry the pics are not the best

Images courtesy Bottomscraper:

Originally Posted by Bottomscraper

I have been using the Globe Blue Run-Dry™ Impellers for years and I have been very happy with them. I usually remove them at the end of the season and they look almost new with a little discoloration. This year every single blade was cracked. I did notice that this year the center appears to be plastic rather than metal like the older ones. Here is a picture of the impeller I removed today after 1 season (about 120 hrs). It has never run dry.

It appears that they have changed materials and that these impellers are now junk. I guess I will be going back to the black ones also. Too bad they had a good product. I was considering using their motor mounts but I think I will look elsewhere.

Just an FYI that the Globe impellers are NOT all they are CRACKED up to be..

[DrB]

I change mine every spring before launch. It's like $8 and about 15 minutes to change. Peace of mind.