Impeller Failure, The Third Kind

[Hudson Force]

I've had the "First Kind" of impeller failure occur when the blades break. Maybe their old and brittle or maybe I've powered over some gritty debris that I raised with my anchor and it's chewwed up the blades.
I've had the "Second Kind" of impeller failure where the soft outside wheel with the blades remains still and the inner metal core spins freely.
....but this "Third Kind" of failure I've never seen before!



Here is a photo of the failed impeller showing the broken metal of the inner core that left the splined axle spinning freely inside without turning the impeller. Have any of you seen this happen before? Do you think this is an electrolysis problem or the quality of the product? You can't see it well in the photo because of the backlighting, but the inner metal sleeve that failed is a gray color, not brass or bronze. What do you think?

[knotnow]

Any chance that the water pump was exposed to freezing temps? The shaft turns but the impellor is froze. We've seen something like that when a customer has dragged is feet a little to long getting his boat in for winterizing. In most cases we've seen accessories hung out from the block freeze first. Like transmission heat exchangers.

[S/V Alchemy]

That sounds very reasonable and reminded me I need to change my impeller.

I wonder if it's Chinese and the metal is something easily eaten in sea water? I thought they were supposed to be bronze.

[zeehag]

pot metal impellers??? wholly forks, beatman---wtf here now-- short longevity factor, mon... ouchies. they best not be pricey. ima get pissed.....

[S/V Alchemy]

Well, it's a theory. It wouldn't be the first time I have picked up some "reasonably priced" bit of boat gear, felt it flex beneath my fingers and muttered "you have got to be kidding!"

[Maine Sail]

Originally Posted by CaptForce

I've had the "First Kind" of impeller failure occur when the blades break. Maybe their old and brittle or maybe I've powered over some gritty debris that I raised with my anchor and it's chewwed up the blades.
I've had the "Second Kind" of impeller failure where the soft outside wheel with the blades remains still and the inner metal core spins freely.
....but this "Third Kind" of failure I've never seen before!



Here is a photo of the failed impeller showing the broken metal of the inner core that left the splined axle spinning freely inside without turning the impeller. Have any of you seen this happen before? Do you think this is an electrolysis problem or the quality of the product? You can't see it well in the photo because of the backlighting, but the inner metal sleeve that failed is a gray color, not brass or bronze. What do you think?

Yes, I have seen it numerous times with Globe brand Impellers.. Can't tell if that is a Globe or not. I stopped using Globe Impellers many years ago after multiple hub failures, short vane life and premature cracking. I have only seen one spun hub in a non-Globe impeller and it was an aftermarket "will fit" impeller for a Sherwood pump. I now try and stick with OEM impellers and while not fool proof, they tend to be more reliable for me.

[Hudson Force]

I'll rule out the failure as a result of freezing,- I've been in Florida and only venture north in the summers. I'm pretty sure this is a Globe impeller and I do know that the spare I put in was a Globe. The new replacement I purchased yesterday is a Jabsco. I'll inspect this current impeller on an earlier schedule. Thanks for the thoughts, Aythya crew

[knotnow]

Originally Posted by CaptForce

I'll rule out the failure as a result of freezing,- I've been in Florida and only venture north in the summers.

Lucky you. The only time I get out of this God Forsaken climate is late fall when I pick up some deliveries south to the islands. You’re right in your assumption that it’s a Globe or some other Chinese import marketed thru another brand.

[barnakiel]

I would imagine if the shaft expands much faster than the sleeve material - gets hot? Or the other way round - very cold water?

b.

[Therapy]

Originally Posted by Maine Sail

Yes, I have seen it numerous times with Globe brand Impellers.. Can't tell if that is a Globe or not. I stopped using Globe Impellers many years ago after multiple hub failures, short vane life and premature cracking. I have only seen one spun hub in a non-Globe impeller and it was an aftermarket "will fit" impeller for a Sherwood pump. I now try and stick with OEM impellers and while not fool proof, they tend to be more reliable for me.

Crap!
I just bought globe to replace my OEMs that only last 60 - 100 hours.
I just lose 2 vanes before it quits moving water.
Westy 30 B three.

[never monday]

Originally Posted by Therapy

Crap!
I just bought globe to replace my OEMs that only last 60 - 100 hours.
I just lose 2 vanes before it quits moving water.
Westy 30 B three.

do you find the vanes plugging the inlet or outlet

[Therapy]

Originally Posted by never monday

do you find the vanes plugging the inlet or outlet

They end up further up the line in the exchanger where the zinc is.

[S/V Alchemy]

This can be avoided by the use of a "basket" type filter past the impeller but before the block. I have caught a number of small objects, such as seaweed, bits of grit, bits of plastic bag, and yes, one time a chunk of impeller vane.

See here: Raw Water Strainers by Don Casey

Now, some people put the Perko/Groco bronze strainer prior to the raw water pump, and I approve. However, this will not keep chunks of the vanes themselves out of the block. Only a post-pump strainer will do this.



So the belt and suspenders approach is recommended, just as most of us have two different grades of fuel filters in two different places in the fuel system.

[Blue Stocking]

Originally Posted by S/V Alchemy

This can be avoided by the use of a "basket" type filter past the impeller but before the block. I have caught a number of small objects, such as seaweed, bits of grit, bits of plastic bag, and yes, one time a chunk of impeller vane.

See here: Raw Water Strainers by Don Casey

Now, some people put the Perko/Groco bronze strainer prior to the raw water pump, and I approve. However, this will not keep chunks of the vanes themselves out of the block. Only a post-pump strainer will do this.



So the belt and suspenders approach is recommended, just as most of us have two different grades of fuel filters in two different places in the fuel system.

I am planning on doing this to my W46, and will step up one size from my raw water pump outlet size, to reduce friction loss and back pressure on the impeller as much as possible.
In July/August the water temp around here gets to 86/87*F, pushing the engine temp to about 200*F, so I dont want to restrict the flow.
My main concern was not impeller failure, but more those damn Sargassum seeds which are about 20 thou larger than my H/E tubes. We carry a bicycle spoke for that solution.