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Author Topic: Raw water pump impeller  (Read 1945 times)

Tom

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Raw water pump impeller
« on: September 06, 2012, 06:04:22 PM »
We'd planned four days on the water last weekend with kids and grandkids. I spent 4 days getting the old tub ready, including washing, maintenance checks, replacing the AGM generator cranking battery and the 8-D engine cranking batteries, topping up and charging the 10 golf cart batteries. When I fired up the big CATs to check them out, the port engine had no cooling water coming out the exhaust port. Nothing new, and something many of us have experienced on an engine or generator sea water pump.

Since I'd previously had all raw water hoses replaced, I realized that the 'dry' hoses didn't allow the water pump to achieve prime, and that the impeller had been fried. I had a spare impeller on board, but I can't get to that pump. I tried several local and not-so-local mechanics, but it was a holiday weekend, and they were either backed up or had their own plans for the weekend.  In a desperate move, Chris squeezed in there, but didn't have the strength to break the bolts loose.

So, the grandkids spent the weekend afloat in our back yard.

Today, one of the guys rang my doorbell. Two hours later he had the spare impeller installed and had tried to find any 'loose' bits of the old impeller that were in hoses between the oil cooler, raw water pump, and aftercooler.

I brought the old impeller up to the house for Chris to put the pieces of the jigsaw together. Attached are a couple of pictures of old, new, and pieces of impeller.

For calibration, the 'good' impeller is approx 3.5" diameter and 4" long.
« Last Edit: September 06, 2012, 06:20:50 PM by Tom »
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Lou Schneider

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Re: Raw water pump impeller
« Reply #1 on: September 06, 2012, 06:20:32 PM »
I'll bet it pumps more water with all of the fins intact!

Tom

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Re: Raw water pump impeller
« Reply #2 on: September 06, 2012, 06:24:10 PM »
LOL Lou, it pumps and infinite more  ;D

One trick the mechanic used that many of us have learned is to coat the new impeller with a liberal amount of liquid soap. When the engine cranks, the impeller has some 'lubrication' until water flows, and soapy water coming out the exhaust is a good clue that the pump achieved prime.
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RLSharp

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Re: Raw water pump impeller
« Reply #3 on: September 06, 2012, 07:37:58 PM »
One trick the mechanic used that many of us have learned is to coat the new impeller with a liberal amount of liquid soap.

Tom,

Back in the day when we had a boat with two small block Chevy engines, it was not uncommon to suck a piece of trash or seaweed over the water intake. As you know it doesn't take long to ruin the pump impeller when the source of water is blocked. I installed pressure sensors on the output of the pumps which would immediately sound an alarm if the water pressure dropped below the set point. Unfortunately, I do not remember what pressure was the trip point for setting the alarm off. We kept our boat on the Genesee River and on two occasions the water intake on the port engine got blocked--the pressure sensor saved the day in both cases.

R
Richard & Linda
Rochester, NY (summer)
Tucson, AZ (winter)

Tom

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Re: Raw water pump impeller
« Reply #4 on: September 06, 2012, 10:44:36 PM »
Quote
I installed pressure sensors on the output of the pumps which would immediately sound an alarm if the water pressure dropped below the set point.

Smart move Richard.
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