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Old 16-04-2016, 15:20   #1
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Generator Water Pump

Mine has just died, it's a Jabsco and obviously death was preceded by seal failures, contamination of bearings and seizure of bearings.
It is a year old, 200 hours, supposedly good pump, yet it is apparently the Achilles heel of a Nexgen generator, My failure is not an isolated one.
So why can't I plumb in a March Airconditioner electric pump that runs whenever the generator in making AC power?
Yes it would have to be below water line down there with the thru hull, but these pumps fun for years and thousands of hours without a failure, and unlike the Jabsco when they go, the don't spray salt water around inside of the generator sound shield before they do. I'm largely upset with the salt water being sprayed around I obviously want that to not happen again.
Now a generator is a constant RPM thing, so therefore constant water supply, so why isn't the March pump used?


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Old 16-04-2016, 16:27   #2
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Re: Generator Water Pump

A very good question the timing of which is extraordinary. My Onan just ate my last impeller and I'm in the Bahamas. My AC pump works fine, if I only had enough hose to plumb it to the Genset I might be set. I would also have to figure out how to get it hooked up so that it always comes on with the genset. It puts out way more water than the genset pump. It might cause a problem with the water cooled exhaust. I wonder if too much flow might cause it to backup into the cylinders/exhaust manifold.
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Old 16-04-2016, 16:49   #3
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Re: Generator Water Pump

It's probably $30 cheaper to buy a Jabsco and the thinking is it must be good as it's fitted to nearly all marinized engines. No electrical wiring costs too.

Its yet another marine part that shouldn't fail quite so often as it does.

And should we really have to pull the thing apart once a year to inspect or change the impeller. An avoidable waste of time and money.
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Old 16-04-2016, 17:43   #4
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Re: Generator Water Pump

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Originally Posted by a64pilot View Post
Mine has just died, it's a Jabsco and obviously death was preceded by seal failures, contamination of bearings and seizure of bearings.
It is a year old, 200 hours, supposedly good pump, yet it is apparently the Achilles heel of a Nexgen generator, My failure is not an isolated one.
So why can't I plumb in a March Airconditioner electric pump that runs whenever the generator in making AC power?
Yes it would have to be below water line down there with the thru hull, but these pumps fun for years and thousands of hours without a failure, and unlike the Jabsco when they go, the don't spray salt water around inside of the generator sound shield before they do. I'm largely upset with the salt water being sprayed around I obviously want that to not happen again.
Now a generator is a constant RPM thing, so therefore constant water supply, so why isn't the March pump used?


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===

I had similar repeated raw water pump failures with a Kohler generator that I bought new. Kohler eventually acknowledged that the original pump had been under spec'd by their engineers and replaced it with a much larger pump under warranty. There was no repayment for the aggravation however. I would keep after Nexgen and try to make a case for something similar. As a point on interest, which Nexgen model do you have?
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Old 16-04-2016, 17:54   #5
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Re: Generator Water Pump

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Originally Posted by poiu View Post

And should we really have to pull the thing apart once a year to inspect or change the impeller. An avoidable waste of time and money.
Not a problem, if I ever have one that lasts a year maybe I'll do that. I put in at least two a year and before I put the check valve in the water intake line i was changing them once a month while cruising. Also there's nothing quite so satisfying as being in the middle of nowhere and finding out (after it's been installed of course) that your last spare was defective and the rubber impeller was not connected to the metal hub.
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Old 16-04-2016, 18:02   #6
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Re: Generator Water Pump

It has been done. There was a particular model of Onan that when the pump seals failed, water leaked into the engine. It was pretty common to replace them with 110 volt continuous duty pumps.

It would be easy enough to try it.
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Old 16-04-2016, 18:58   #7
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Re: Generator Water Pump

I have contemplated such a change with our generator as well but have not yet done anything about it as we now have two pumps, one on the motor and a spare although ours are not Jabsco but another manufacture. Jabsco pumps are normally quite robust although the impellers need be replaced at 100 hour intervals and the lip seals at (supposedly) 500 hours. Given that, you might want to contact Jabsco about the matter to see what their tech boys think/can tell you. In any case, a March 120v magnetic drive would be a good alternative so long as the water throughput matches or modestly exceeds the throughput of the Jabsco at the normal operating RPM of your generator.

FWIW...
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Old 16-04-2016, 21:29   #8
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Re: Generator Water Pump

I think I will give it a try maybe next weekend, March pump should be way more volume, but I'll install it and see, easy enough to install with a ball valve if I need to decrease flow a little.

I have the little 3.5 KW Nexgen, I don't see anything wrong with their installation, the pump isn't being overdriven, with reduction ratio, looks like it's driven at less than 1000'RPM, ,I guess I Could count teeth and figure it out.



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Old 16-04-2016, 21:34   #9
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Re: Generator Water Pump

Be sure to put the valve on the discharge side of the pump. It's ok to restrict the discharge but you don't want to restrict the intake.

Let us know how it works.
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Old 16-04-2016, 23:14   #10
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Re: Generator Water Pump

Short answer is you can.

Attached below is a picture of a little (3.5) Phasor generator that I rebuilt last year, with an attached 24vdc Harbour Freight rotary vane pump, running at about 3/4 load, in this picture for about 45 minutes.

The original setup from Phasor was to use a 110 volt pump that came on when the generator end came on.

Since the 110v pump that came with the generator when I inherited it was (and still is) being used as a booster pump for my 8 psi artesian well when taking showers, and a comparable one from Depco was about 400.00, I figured I would try the 40.00 solution.

The only difference in the original setup is that in the plastic junction box added to the end (in which were also included a couple of 110 outlets and a circuit breaker), I added a 110 v relay that activated when the generator kicks in, which in turn actuated the 12v pump through the DC start circuit, thus giving a (slight) delay before water started pumping.

There is an obvious potential problem (and I believe Phasor has since gone to an engine driven pump for this model) with flooding, and it is apparently a known issue. The reason the generator was rebuilt was because of upper cylinder corrosion, the person I sold the generator to had the same problem, and there was a thread in the past couple of years here about another with an identical issue.

I think that what happens is when the engine shuts down the residual momentum of the generator keeps the pump running long enough so the water pressure is high enough to overcome the air pressure from the non-combusting but still rotating engine to allow enough water or water vapor to be drawn into the cylinder to cause problems. Complicating the issue is the fact that the engine is horizontal and the exhaust port is above the intake port, so any water present drains back into the cylinder.

That's not to say that the problem couldn't be solved by a redesign of the raw water/exhaust system, or some kind of automatic timed shutdown cycle, or even a manual pump switch. Or that the combined air pressure of a multi cylinder engine wouldn't be enough to alleviate the issue.

I'd give it a try.
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Old 20-04-2016, 05:23   #11
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Re: Generator Water Pump

Quote:
Originally Posted by a64pilot View Post
I think I will give it a try maybe next weekend, March pump should be way more volume, but I'll install it and see, easy enough to install with a ball valve if I need to decrease flow a little.

I have the little 3.5 KW Nexgen, I don't see anything wrong with their installation, the pump isn't being overdriven, with reduction ratio, looks like it's driven at less than 1000'RPM, ,I guess I Could count teeth and figure it out.



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Just to point out the obvious. An engine driven pump doesn't deliver water when the engine isn't running, neither should the independently driven pump. You don't want to fill the water lift muffler and then back water up to the cylinders. Time the start of the electric pump AFTER the engine starts and stop it at the same time the engine stops.
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Old 20-04-2016, 05:42   #12
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Re: Generator Water Pump

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Originally Posted by DotDun View Post
Just to point out the obvious. An engine driven pump doesn't deliver water when the engine isn't running, neither should the independently driven pump. You don't want to fill the water lift muffler and then back water up to the cylinders. Time the start of the electric pump AFTER the engine starts and stop it at the same time the engine stops.
Thats right, you have to think about that. Its a very important point.

The main reason that impeller pumps on generators don't last is that they run sometimes with no water and get hot.

How long does your impeller last?
It should last for more than 500 hours, if not you have water lubrication problems which also wear out your pump seals.

If you want your impeller to last more than 500 hours then the impeller must not run dry at all even for 1 second at start up. That means that the impeller must immediately suck water at every startup.
The generator must also have a sensor that detects no water at the pump and switches off the generator immediately.

If your generator satisfies these 2 conditions then your impeller will last more than 500 hours and your pump seals and bearings will also last a lot longer.
Even 1 run dry resulting in impeller blade damage is enough to damage the pump.
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Old 20-04-2016, 05:50   #13
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Re: Generator Water Pump

Quote:
Originally Posted by a64pilot View Post
Mine has just died, it's a Jabsco and obviously death was preceded by seal failures, contamination of bearings and seizure of bearings.
It is a year old, 200 hours, supposedly good pump, yet it is apparently the Achilles heel of a Nexgen generator, My failure is not an isolated one.
So why can't I plumb in a March Airconditioner electric pump that runs whenever the generator in making AC power?
Yes it would have to be below water line down there with the thru hull, but these pumps fun for years and thousands of hours without a failure, and unlike the Jabsco when they go, the don't spray salt water around inside of the generator sound shield before they do. I'm largely upset with the salt water being sprayed around I obviously want that to not happen again.
Now a generator is a constant RPM thing, so therefore constant water supply, so why isn't the March pump used?


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I've always found March pumps to be incredibly fun too... I didn't want to say anything because people would think I'm a weirdo... (or more than they do) Kudos for coming out Mr. Pilot...


Quote:
Originally Posted by DotDun View Post
Just to point out the obvious. An engine driven pump doesn't deliver water when the engine isn't running, neither should the independently driven pump. You don't want to fill the water lift muffler and then back water up to the cylinders. Time the start of the electric pump AFTER the engine starts and stop it at the same time the engine stops.
Wired to the gen output Dot !
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Old 20-04-2016, 06:21   #14
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Re: Generator Water Pump

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Originally Posted by Fuss View Post

The main reason that impeller pumps on generators don't last is that they run sometimes with no water and get hot.


If you want your impeller to last more than 500 hours then the impeller must not run dry at all even for 1 second at start up. That means that the impeller must immediately suck water at every startup.
.
I'm currently installing a generator and I noticed that nothing in the manual addresses this. The manual has a lot of info related to not getting siphons etc. that would flood the engine.

My generator is above the water line so I shouldn't need an anti-siphon in the line. But I installed one anyway as both a safety measure and as a way to know that the water pump at least always has water available in the discharge leg that would be able to lubricate the pump on start-up.
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Old 20-04-2016, 06:38   #15
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Re: Generator Water Pump

Is there a way to have the intake hose be above the pump prior to the pump to maintain some water in the hose and pump? I have found almost all my impeller type pumps failed due to being run dry on start up because of drain back and as the pump wears it is less capable of priming it's self leading to further damage
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