Tuesday, January 3, 2012

Recovering Distorted Raw Water Impeller

Reverse stress stake out
Some of us have left our boat for a season with the raw water pump impeller left in. Upon our return and check of the impeller, before puting the boat back in the water, we discover the impeller blades are permanently deformed and in some cases the deformed blades do not always touch the side of the pump body as it is rotated. I have also found the same to be true for new pumps I have purchased for spares. The pump has been sold with the impellor already inside, and who know how long it was sitting on the shelf. So, I remove the impeller and in the past have just thrown it out and either replaced for the pump to be used, or kept the new one outside the pump, and stored pump and new impeller in a zip lock bag, in my spares compartment.
Now, after I remove the impellor and  give the blades a good inspection for deterioration, I stake it out on a piece of wood with nails and distort the offending blades back in the opposite direction. I leave this for a few weeks/months until the blades look close to "normal" again.
You can see here to the left, an impeller that has about 3 weeks in it's reversed stress position and the blades are almost now at right angle to the body. This would probably be OK to reinstall, but will be given some more time.
If the impeller came from the raw water pump  about to be used. I just put in a new one to get the boat going, and place the "recovered one" into spares as it becomes "UN-distorted:"
This  trick should save me some money. I hope it does for you too!

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