Be Wary (Maybe) of Stay Cool Pumps Impellers

[NoTies]

You can cross the road without looking multiple times without getting run down also but do you risk it? You can also install rubber impellers incorrectly multiple times without a failure.

[Jim Cate]

temporarily softens the rubber to allow more flex in the blades (rather than yanking hard blades tight with a zip tie like some do)

Pete, can you provide some documentation for this? I don't believe that wiping some glycerin on the rubber reduces stiffness at all... it serves to reduce friction during installation and in first startup, yes indeed, but hard to see how the other is accomplished.

And one does not bend the blades further during installation than they are bent in use by the cam.

Jim

[Jim Cate]

Originally Posted by a64pilot

Doesn’t come with a stay cool impeller
But then neither did an O ring.
In truth I don’t remember using a lube, I will sometimes use some dish soap to make installation easier, but any lube is gone almost instantly.
For some installations, like some generators where the pump is above waterline, the lube may be somewhat critical, but my pump is just below waterline so it’s full of water before I start the engine.

The replacement Yanmar branded impeller, that I know is old, but don’t know how old, didn’t come with any lube either, and none was used, and it’s working fine. I ran it several hours, and then removed looking for old impeller bits.Attachment 183616

Yanmar impeller left, 9 blades .142” thick
Stay Cool right, 12 blades, .093 thick

Don’t know the significance if any from having more, but thinner blades

It's hard to tell from the photo, but the blades on the sta-cool look shorter and its hub larger in diameter than on the Yanmar model. I wonder if that wouldn't explain the failure... kinda mashing the blades excessively as they pass over the cam. Could it be the wrong model for your pump?

Jim

[Simi 60]

Originally Posted by a64pilot

.

What's all that other brown gunge?
Almost looks like incompatable coolants?

[wsmurdoch]

The Yanmar impeller for my Yanmar 3HM35F says JOHNSON and 827 in raised markings in the rubber between the roots of its blades.

The heat exchanger on my engine is 3 pass on the tube side (fore to aft, back forward, then finally back aft). I occasionally rod out the tubes with a 22 cal rifle cleaning brush.

Removing the heads from my exchanger does not contaminate the engine coolant. The coolant is on the shell side of the exchanger and the seawater is on the tube side.

I once had a coolant blockage that was caused when the corroded end of a zinc pencil anode came loose and blocking the flow when it lodged when it attempted to enter the barb end of a hose-to-NPT fitting.

Bill

[Simi 60]

Originally Posted by mikecambrai

Thanks, DRCAT for your comments. I have not been able to source a pump of 2000l/hr yet in Europe but will keep trying.
I think that I will set up a jury rig bypassing the Jabsco, and just see what happens. I need to find out if this type of pump can cope with the vagaries of my engine in the marine environment.
2000l/hr is the correct flow for a 100 HP engine.

MD30 are continuous rated @ 1980 lph

https://www.ebay.com.au/itm/Resun-MD...edirect=mobile


MD40 are 3000lph

https://www.ebay.com.au/itm/Resun-MD...edirect=mobile

I have the MD30 as a replacement for my genset impeller pump when it next needs a rebuild, but a genset is constant rpm.

I would be concerned of constant flow water on an engine running through various rev ranges.
I know Gardner diesels run a centrifugal pump but their rpm/ flow is controlled and matched to the engine rpm.

[a64pilot]

While I do not know the type of plastic or rubber used in an impeller, I can assure you it’s not going to be softened in a minute or two from glycerine.
In fact I’d bet glycerine is picked as it doesn’t have an effect on the material, where hydrocarbon lubricants may.
If they wanted it softened as in made more pliable, that is often done by warmth, placing in hot water, not chemically.
However if you look at how compressed an impeller is and think of how they have to work in very cold water, and repeatedly get smashed like that likely millions of times, they have to be very resilient, and pliable.

When installing “Rubber” sleeves on the long tail rotor driveshafts of an OH-58 helicopter, we used “surgical lube” AKA KY jelly for the exact reason it had no effect on the material, but without some kind of lube you would never get the sleeves to slide down the driveshaft.
Used Crisco cooking grease to hold fuel O-rings in place for the same reason, no effect on the material.

[a64pilot]

Good eye Jim, the center hub on the stay cool measures 1.412”
The Yanmar measures 1.230”
I have no idea if that is relevant though.

Box says it replaces the correct part number

[Jim Cate]

My goodness, Pete, what an angry response to a request for some information to support your claim.

At any rate, I read through your interesting linked dissertation, and I now know a lot more about glycerin (or glycerine) than before. Fascinating stuff, it turns out, with an incredible number of uses. However, nowhere in that vast body of information did it say that it increased flexibility of rubber products when externally applied. It does affirm that glycerine is a good lubricant for rubber, something that we seem to agree upon.

And with respect to your first sentence above, one would think that the knowledgeable professional with 40 years of experience would be happy to educate the poor amateur practitioner, who suffers from ignorance on so many subjects. Perhaps I was wrong to ask.

Jim

[NoTies]

Originally Posted by Jim Cate

My goodness, Pete, what an angry response to a request for some information to support your claim.

At any rate, I read through your interesting linked dissertation, and I now know a lot more about glycerin (or glycerine) than before. Fascinating stuff, it turns out, with an incredible number of uses. However, nowhere in that vast body of information did it say that it increased flexibility of rubber products when externally applied. It does affirm that glycerine is a good lubricant for rubber, something that we seem to agree upon.

And with respect to your first sentence above, one would think that the knowledgeable professional with 40 years of experience would be happy to educate the poor amateur practitioner, who suffers from ignorance on so many subjects. Perhaps I was wrong to ask.

Jim

Obviously you missed the bit about it being a plasticiser. Still, it appears arrogance rather than facts are what counts when it comes to the pilot.

[Jim Cate]

Originally Posted by NoTies

Obviously you missed the bit about it being a plasticiser. Still, it appears arrogance rather than facts are what counts when it comes to the pilot.

Plasticizers are part of the original composition of the material, not something that you rub on the outside. And no, I didn't miss that in the article.

Jim

[Sailmonkey]

Originally Posted by Simi 60

What's all that other brown gunge?
Almost looks like incompatable coolants?

Ummmm, that’s the seawater side....and the gunge is the fluid level when the engine is off.

[NoTies]

Obviously my replies will be deleted so I cannot offer any more facts.

[Jim Cate]

Originally Posted by a64pilot

Good eye Jim, the center hub on the stay cool measures 1.412”
The Yanmar measures 1.230”
I have no idea if that is relevant though.Attachment 183618

Box says it replaces the correct part number

I wonder if the larger hub diameter changes the way the vanes are mashed by the cam? All conjecture, of course, but such an early failure must have some cause, and i doubt if initial lube or lack thereof would be it.

Jim

PS: Can you somehow measure the radius from the center of the impeller to the outside of a "squashed" vane on each one? If the Sta Cool's radius is a bit larger, perhaps that increases the shearing load on the root of t he vane.

[a64pilot]

Measuring the inside of the pump requires disassembly of the pump of course, something that I’m unlikely to do just to learn more about it.

However I doubt that it’s too tight, cause if it was then it would have been really hard to install, and I don’t remember it being real hard, about the same.
However with the center hub being larger, then of course the blade has to be deflected more, and if indeed there is very little room, that would I think lead to failure of the blades from fatigue I think.
I never noticed the diameter difference I have to admit, you saw it in the photo and I didn’t even with both of them in my hand.

I have to think though that I either got a bad example, or something happened like a plastic bag or similar that could just fall off on its on.
Otherwise surely others would have had failures and been chiming in, but no one has.
Leads me to believe one of two things, either use of these impellers is very uncommon, or that my failure was a rare occurrence.
I’m not believing however that not applying glycerine that wasn’t included with the impeller, nor mentioned in the brief instructions has anything to do with it.

Maybe I’ll call the manufacturer and ask?