Are all impellers made equally?

My engine does approximately 150 hours each year. The boat is only in commission for seven months, and laid up ashore for the winter. Once ashore, I take out the pump impeller, have a close look at it, and normally store it before refitting it in the Spring. I reckon I am perfectly capable of detecting any signs of cracking etc, which could lead to blade failure. If you feel unsure of your ability to check the condition, then go ahead and change it. The choice is yours, but at least check it, and always carry a spare.

If you are unlucky enough to find that an impeller has lost a blade, consider where it will have gone, and find it. Clue, it'll be at the end of the tube stack in the heat exchanger.
 
Stemar said:
Engine and water pump manufacturers have to be conservative in their estimates of impeller life. If they say every year, that means they expect as near as dammit 100% of impellers to last a year. That implies a mean time between failures of 3 years or more.

I reckon on a fairly conservative maintenance schedule - check and replace if necessary, simply because the consequences of losing a blade somewhere inside the engine are not something I want to have to deal with.
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It won't be in the engine, it will be in the heat exchanger.
 
doug748 said:
I don't buy Johnson impellers, which used to break up annually.
Jabsco, in my size -653001, never do and the present one has just started to show signs of stress after 4 years and c400 hours
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I probably have the same impeller (part no 18653-0001). It is taken out and inspected after lift out every autumn, stored during the winter months and reinstalled in spring.
The original impeller of my 2005 Beta engine was retired after seven years service, although I could see nothing wrong with it (kept as a spare).
Now I have had another seven years from my second impeller – I guess it is time to retire this too.
May I then claim to be doing preventive maintenance on a seven year cycle?

(NB low engine hours, ≈ 50/year)
 
Interesting - I replaced Impeller this spring with a Johnson spare and when we were in Holland for our summer cruise, the engine overheat alarm sounded just as we were approaching a lock, managed to veer off and dropped anchor. Checked the Impeller and all the vanes were split at the hub and about to disintegrate. Fitted a spare Impeller and everything ok. Managed to get another Johnson Impeller at the next stop. I was most surprised as in my experience they usually last 3 - 4 years.
 
Stemar said:
I reckon on a fairly conservative maintenance schedule - check and replace if necessary, simply because the consequences of losing a blade somewhere inside the engine are not something I want to have to deal with.
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PaulRainbow said:
It won't be in the engine, it will be in the heat exchanger.
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Only if you have a heat exchanger! :)
 
Rogershaw said:
Anyone used a run dry impeller.

https://www.amazon.com/Globe-Marine-Run-Dry®-Impeller-6760-0003/dp/B00C9KGSB4
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After reading the single review, I'm not sure that I want to:

Global impellers are sold under “Run-Dry®” marketing pitch.
Think about it: why would you want to run your engine without cooling for 15 minutes???!!!
These impellers have very poor self-priming ability and wear off much faster than OEM.
Here is my story:
I’ve purchased an impeller sold by Globe Marine Products on Amazon on August 21, 2017 and installed In March 2018.
The engine was commissioned in May 2018 at the beginning of summer sailing season.
During summer sailing season I’ve experienced numerous problems with engine
raw water pump self-priming after moving under sail with engine off.
There was no water coming out of exhaust.
Raw water pump is located bellow water line and no hoses, fittings or strainers are
reaching above water line when the boat is leveled.
In order to make raw water pump work, I had to loose pump cover plate to let air out,
Sometimes it had to be done several times.
I never had this kind of problem while using OEM impeller: 15 years of ownership with extensive cruising
Between NY and Miami, Bermuda, Bahamas and Caribbean.
Finally, while sailing South in October 2018, I was not able to prime the pump at all.
A couple of miles offshore, I replaced Globe Marine impeller with used OEM impeller and everything worked fine!
Has been sailing in various conditions for two weeks since and had no problems at all.
If you examine attached pictures, you’ll see how badly Globe Marine impeller tips are worn
Comparing to OEM impeller with over 3 times as much usage.
Also, I observed that the engine was running hotter above 2100 RPM (Volvo Penta MD17D, Max RPM 3000)
Not exactly overheating, but closer to red than before)
I suspect that because Globe Marine impeller blades are softer, they don’t seal as well as OEM,
Which can contribute to weaker raw water flow and, therefore, higher engine temperatures.

If you still want to try this product, watch exhaust water obsessively and monitor engine temperature.
Make sure that you have time, sea room and ability to purge the pump or replace impeller when you start the engine.

:ambivalence:

Richard
 
After three years of ownership I realised that I had never thought about the impeller. Water exited from exhaust with gusto!

Three blades missing; so with an engine service I found six blades in the heat exchanger!

Lesson learnt :)
 
I bought a spare impeller for my Bukh from French Marine a while back. I initially didn't take any notice of the fact it was labelled as (IIRC) nitrile. I later read that this material is preferred for applications (such as bilge pumps, etc.) where there was a risk of contamination by diesel and other oils, as standard impeller material is degraded by these, but also that nitrile was (relatively) intolerant of running dry.

In my application - seawater pump - there is very low risk of oil contamination, but the key risk is running dry through blockage (or forgetting to open the seacock). Should I be worried about using this impeller?
 
There is a company that makes aftermarket silicone impellers for all kinds of pumps. Jabsco include. They claim their impellers are temperature resistant which comes in handy if by accident you run it dry.
 
PaulRainbow said:
It won't be in the engine, it will be in the heat exchanger.
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LittleSister said:
Only if you have a heat exchanger! :)
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I don't, it's raw water cooled.

One of the consequences I have in mind is a lee shore with the temperature alarm screaming at me. Snapdragons were never the best boat hard on the wind, and above a good 6, any real progress to windward under sail is unlikely, especially with a lumpy sea.
 
Impeller materials vary. Jabsco (I believe) uses neoprene, which has a good flex life but does not tolerate propylene glycol well. Others use nitrile (not as good a flex life) or EPDM (cannot tolerate any oil).

In the case or neoprene, winterizing with propylene glycol (most pink AF); a single winter can ruin the impeller, even if it has never been used. Either reinstall in the spring or use ethylene glycol, which does not affect neoprene. It is not a potable water system, so EG is OK.
 
thinwater said:
Impeller materials vary. Jabsco (I believe) uses neoprene, which has a good flex life but does not tolerate propylene glycol well. Others use nitrile (not as good a flex life) or EPDM (cannot tolerate any oil).
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This has the smack of truth thinwater. The Johnson impellers, that regularly broke up after less than 12 months use, felt noticeably harder and less flexible.

The Jabsco alternatives, that I now use, would not suffer from my random use of anti freeze as I immediately remove them for inspection after running winter mixture through the raw water circuit.
 
PaulRainbow said:
Various engine service schedules specify that the impeller must be changed annually or every xx hours.

Curiously, different engines/manufacturers will specify different schedules, but they will be using the same water pump. There is no logic behind having to change an impeller annually in one engine, when the same impeller in another engine has a 4 year schedule.
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Yes, why would different engine manufacturers specify different maintenance schedules for Jabsco water pumps?

Maybe the design of some engines require a higher flow rate so they run the Jabsco faster? Maybe the pressures are different on some engines and therefore put more stress on the impeller blades? Why are there X6 blades on some impellers yet X8 on others?
"Johnson Pump engine cooling pumps are designed to the demands of engine manufacturers a....

This is an interesting Johnson pamphlet.

Jabsco Impellers are manufactured in rubber compounds selected for their chemical compatibility:
Neoprene Longest life, good long-t erm flow control
Hygienic Food-grade to US 3A
Neoprene Standard 18-02 and FDA
Nitrile Excellent resistance to oils
EPDM Best for hot water-based fluids and CIP cleaning temperatures Food Grade to 3A and FDA standards
Viton® Excellent chemical resistance but lower performance and shorter li

https://www.spxflow.com/en/assets/pdf/JP-impellers_810_GB_A4_2018-03.pdf
 
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