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Old 09-04-2013, 14:11   #1
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Quite awhile ago I purchased a spare March pump to convert my 1985 11kW Westerbeke from a gear driven impeller pump to an AC powered pump. To be installed when the standard pump shaft started leaking, they all do eventually. It's in a bad place, I have to unbolt the entire generator and slide it away from the wall to even change the impeller.

I had hoped it would do this somewhere where I could have a plate made to cover the hole where the geared pump attaches to the accessory gear. But of course Im in a place where that is questionable at best, and it's leaking.

The question is, if I remove the Impeller, route the raw water around, not through the pump, can this shaft just spin? It will no longer have any cooling from the raw water flow, and I wonder if the bearings are OK that way. I can shoot it with an IR gun, but how hot is too hot?

I may look at removing the gear from the shaft of the impeller pump, but don't know if it comes off or not. Yet...

Thanks, Bob
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Old 09-04-2013, 19:27   #2
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Re: AC Powered Raw Water Conversion

IIRC, those pumps have sealed, single row ball bearings, which are likely rated for a lot higher rpm than they get. without the impeller load on the shaft, there should be very little heat generated at the rotational speeds that pump will see. On the other hand, if the seal has been leaking, and salt water has gotten into the 'sealed' bearing, then corrosion could be setting in already and you will eventually have the bearing seize up entirely. you should be able to tell pretty easily by taking the pump off, removing the impeller and rotating the shaft by hand. if it's smooth and rotates with no hard spots or stickiness or bumps, you should be fine.

shooting with an IR gun when running the first few times is of course a good idea too. I wouldn't be worried unless I saw it getting too hot to hold a hand on it.

my 2Cents!

good luck-
bg
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Old 09-04-2013, 19:35   #3
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Quote:
Originally Posted by NSboatman View Post
shooting with an IR gun when running the first few times is of course a good idea too. I wouldn't be worried unless I saw it getting too hot to hold a hand on it.

good luck-
bg
This must be a scientific mechanic test, it's too hot if you can't keep your finger on it for a few seconds. One of my DeFever friends told me the same thing offline....

Thanks, Bob
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Old 15-04-2013, 11:50   #4
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Re: AC Powered Raw Water Conversion

Old Snipe Test:
Bare hand on "warm" surface for 3 seconds (one Mississippi, two Mississippi, three Mississippi, ow!!) before you have to pull your hand away: surface is at 130-135F.

Old Snipe
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Old 15-04-2013, 12:31   #5
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Well...I completed the install. When I pulled the pump to get a good look at it, I found a ball bearing on the gear side of the pump in perfect condition. It gets an oil bath from the accessory gearbox. So it's a bit warmer than that, but runs the same temp as everything else. I'm sure it won't do anything for the wet side seal, but it was already leaking...

So far so good. The centrifugal pump moves a little more water than the old impeller one did judging on the water exiting the wet exhaust.
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