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Old 23-04-2016, 11:23   #16
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Re: Stumped by waterpump

Could be a collapses hose (internal part) clogged sea strainer or a clogged port in the discharge elbow.
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Old 23-04-2016, 11:26   #17
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Re: Stumped by waterpump

Good advice given but one more .... I once had a new impeller that had lost the bond between the rubber and the bushing, it looked good but the bushing would turn without turning the vanes.
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Old 23-04-2016, 12:18   #18
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Re: Stumped by waterpump

I vote for an air leak. It's much easier to suck air than water. I've seen this issue with several engines and pumps. Even a pinhole air leak can stop pumping.
MY current impellers (2 Detroit mains, 2 generators, Perkins and Onan) are 5 years old.
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Old 23-04-2016, 16:43   #19
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Re: Stumped by waterpump

For those of you that do not want to read any further, it's fixed. For the rest of you, here is the saga.

I took off the hose from the thru hull and the water flowed freely. I put the hose back and took the top off of the strainer, water flowed freely. Everything else is above the water line, so I put a hose from the washdown pump to the hose coming off of the strainer and water flowed freely all the way to the pump. Also there were no leaks between the strainer and the pump. But this was under pressure not suction. As it happens I have a small manual vacuum pump on board (I have Way too much stuff on this boat). So I found a fitting and put it into the end of the hose at the pump and pumped the hose full of water. When I stopped pumping the pressure held at -3.5 inches of Mercury (iM). This is about right as the end of the hose was about 40 inches above the water line. It held that vacuum for 10 minutes, so no leak in the intake system. So it must be the pump right. I plug the outlet and pull 25 iM vacuum on the pump. It holds!, no leak in the pump (hold that thought). I then put the vacuum pump on the outlet of the pump and pulled the prime all the way through the pump and into the outlet hose. It pumped what was in the pump and the outlet hose and stopped. I thought it must be the hose to pump connection, so I trimmed off an inch of hose to get on nice clean rubber. No change. put in another impeller and still no change. By this time i'm in insanity mode, that is repeating the same things over and over again expecting a different result. I tried disconnecting the outlet in case things were blocked on that end and still no change. It would empty the water out of the pump but that was it. It seemed it had to be a suction side air leak but the vacuum pump tests said no. I was talking to a friend of mine and he said maybe you have a bad bearing. It wasn't obvious, but that is what it ended up being. I took the pump apart and the shaft had about 1/32 of play radially. The bearing had indeed gone bad, even though it wasn't making any noise that I could hear. It so happened I had kept many of the parts to my old water pump when I replaced it with this one two years ago. The shaft and bearing assembly from that one had no play in it at all. I took the new pump hosing off the mount and put it on the old shaft/bearing. It now pumps water. Apparently that small amount of play caused an air leak at the shaft seal but only when at operational speed. The static testing showed no sign of it.

I suspect I might have the belt too tight and it caused the wear in the bearing. In any case I see a new pump in my near future but am operational for now.
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Old 24-04-2016, 08:51   #20
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Re: Stumped by waterpump

Thanks for the recap Bill.

That is helpful for us all.

Glad you are fully operational again.

Cheers!

Bill
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Old 24-04-2016, 09:27   #21
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Re: Stumped by waterpump

Thanks for the description Bill. Good detective work.
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Old 24-04-2016, 11:19   #22
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Re: Stumped by waterpump

This is why there is the old saying "It works, don't touch it."


I'd have to suspect that the old impeller, being old and stiff, was actually acting AS a bearing, keeping itself and the shaft in the correct centered position. Replaced with a new impeller, which was more flexible, that allowed the wobbling shaft to misbehave.


A most unexpected situation and the kind of thing that drives even professional mechanics NUTS.


Kudos for resisting the temptation to simply get out a bigger hammer!
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Old 24-04-2016, 13:51   #23
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Re: Stumped by waterpump

Thanks for posting the solution. One more thing to try to remember if I encounter a similar situation. I doubt I would have thought of that as the cause in 100 years.

By now I probably would have stripped the pump and replaced every part but the housing.
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Old 24-04-2016, 14:57   #24
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pirate Re: Stumped by waterpump

Folks have bought new boats for less.
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Old 24-04-2016, 15:03   #25
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Re: Stumped by waterpump

Quote:
Originally Posted by hellosailor View Post
This is why there is the old saying "It works, don't touch it."


I'd have to suspect that the old impeller, being old and stiff, was actually acting AS a bearing, keeping itself and the shaft in the correct centered position. Replaced with a new impeller, which was more flexible, that allowed the wobbling shaft to misbehave.


A most unexpected situation and the kind of thing that drives even professional mechanics NUTS.


Kudos for resisting the temptation to simply get out a bigger hammer!
The old impeller broke off three vanes, it was not preventative maintenance.
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Old 24-04-2016, 15:30   #26
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Re: Stumped by waterpump

Had exact same problem with my Oberdorfer seawater pump which is less than 1 yr old. My brother said to smear some cup grease on the inside of the cover plate. Started working fine. Apparently these things need to be 101% airtight or they won't prime.
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Old 24-04-2016, 15:47   #27
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Re: Stumped by waterpump

Quote:
Originally Posted by Cal31 View Post
Had exact same problem with my Oberdorfer seawater pump which is less than 1 yr old. My brother said to smear some cup grease on the inside of the cover plate. Started working fine. Apparently these things need to be 101% airtight or they won't prime.
You should also assure that the inside of the faceplate on that pump is flat, flat, flat.
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