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Old 12-05-2016, 17:01   #1
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No Raw Water Flow To The Generator

I have a Paguro 4000 generator onboard that is not getting any raw water flow.
1. The sea cock is open
2. I can blow air through the intake hose at the strainer and hear air escaping underneath the boat.
3. If I remove the impeller and cover, I can blow air from from the strainer through to the pump, so I know the hoses are clear.
4. The strainer is clean
5. I replaced the impeller twice with the same affect. The impeller appears to be seated properly and is undamaged.

I do not see any raw water in the strainer when the generator is running, and the generator soon shuts down as it starts to over-heat.

Any thoughts?
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Old 12-05-2016, 17:13   #2
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Re: No Raw Water Flow To The Generator

clogged mixing elbow, or clogged heat exchanger.

try blowing from the pump discharge through the heat exchanger and into the exahust
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Old 12-05-2016, 17:29   #3
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Re: No Raw Water Flow To The Generator

Quote:
Originally Posted by enjaku View Post
I have a Paguro 4000 generator onboard that is not getting any raw water flow.
1. The sea cock is open
2. I can blow air through the intake hose at the strainer and hear air escaping underneath the boat.
3. If I remove the impeller and cover, I can blow air from from the strainer through to the pump, so I know the hoses are clear.
4. The strainer is clean
5. I replaced the impeller twice with the same affect. The impeller appears to be seated properly and is undamaged.

I do not see any raw water in the strainer when the generator is running, and the generator soon shuts down as it starts to over-heat.

Any thoughts?
Prime the sea water system and try again, my guess is that there is too much air in there.
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Old 12-05-2016, 17:47   #4
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Re: No Raw Water Flow To The Generator

There are so many variables with a problem like this. Anyway, here goes.

Maybe your raw water pump is sucking air but where from? Replace all of the hose between the seacock and the pump. If that fails replace the impeller. If that fails replace the gasket which seals the cover of the raw water pump.

That'll do for now.
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Old 12-05-2016, 19:11   #5
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Re: No Raw Water Flow To The Generator

Oddly enough I had the same problem on an onan raw water pump and had a thread about it going 3 weeks ago. The problem ended up being a bad bearing in the water pump shaft. This allowed the shaft to wobble about 1/32 of an inch which caused an air leak at the mechanical seal on the water pump shaft. I went so far as to put a vacuum pump on the outlet to prove I could such water through the system and still could not get water flow by running the pump. This was because the seal only leaked when the pump was rotating at high speed. At slow speed the spring on the mechanical seal was strong enough to overcome the wobble and hold the seal. I don't know if your pump is belt or gear driven, but if there is any play at all in the shaft the bearings are gone and the seal will leak air when turned at operating RPM. I hope this helps.
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Old 13-05-2016, 05:36   #6
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Re: No Raw Water Flow To The Generator

I suspect there is air throughout the system. The generator has less than 800 hours on it, and all of the pipes look to be in really good shape. I'll try priming the system better and see what that brings. Thanks all. Mucho appreciated.
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Old 13-05-2016, 07:52   #7
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Re: No Raw Water Flow To The Generator

If the pump has been running dry long enough for the motor to overheat then the impeller will likely be shot with possible damage to the pump.
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Old 13-05-2016, 08:26   #8
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Re: No Raw Water Flow To The Generator

Like Capt Bill, we had the same issue with an Onan raw water pump. The mechanic could find nothing wrong)impeller, bearings, etc, but noted the wear plate and the pump interior looked worn. Turned out the pump body was worn enough that it would not suck water. Even if we primed it, it would run and pump water for a few minutes, and then quit. We bought a new pump asembly (not cheap!), installed it, and have had no problems since(3+ years).
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Old 13-05-2016, 09:39   #9
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Re: No Raw Water Flow To The Generator

when did this happen, after a impeller change or just stopped when in use, if as you stated all lines are clear. might want to hook up a water hose from the dock at low pressure from the pump hose to the engine run engine and see if you get discharge water. if ok reconnect hose to pump and recheck impeller, put some dishwasher liquid in the impeller will help pump suck in water.
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Old 13-05-2016, 09:57   #10
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Re: No Raw Water Flow To The Generator

For us, the genset was working fine, we shut it down and sailed to the next destination....we were cruising in the Italian Medd. when we got in at Syracuse, and got the pick set, we went to start the genset, and that's when we noticed there was no water coming out of the exhaust. I tried every trick I knew, nothing worked, so we went into the local marina and went looking for a mechanic.....but that's a whole other story!!!
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Old 13-05-2016, 10:02   #11
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Re: No Raw Water Flow To The Generator

previous suggestions are all good. start simple!! check the pump cover for wear, if there are grooves lap it smooth and try again. If it still doesn't work pack it oath grease and try if it pumps and stays pumping, good. if not check the exchanger. If the mixing elbow was that clogged, you'd have a restriction in the exhaust flow too...hard starting low rpms. If it won't re-prime on a second round the pump is bad in some way...ie...shaft seal/ bearing, worn housing.....

Good luck, check the easy stuff first, it's less expensive.
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Old 13-05-2016, 10:09   #12
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Re: No Raw Water Flow To The Generator

I had raw water pump issues with my gen, different brand, probably different size too.
But anyway I ended up removing my mechanical pump and replacing it with an electric March pump usually used to supply water for airconditioners. My reasoning is they require zero maintenance, can't leak inside of the generator sound shield and seem to run for years without failure.
So far it has worked fine, too early to declare victory, but it's my understanding that this is not an uncommon mod
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Old 13-05-2016, 10:12   #13
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Re: No Raw Water Flow To The Generator

I don't know about your genset and water pump, but on our engine (Volvo) there is a plastic piece that connects the engine to the water pump impeller. I suppose this piece is supposed to break and avoid damage if the pump seizes. A spare was included when I bought my boat.


Take the cover off the water pump and hit the start button. Watch to see if the impeller turns. Just do this long enough to see if it's turning.
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Old 13-05-2016, 10:26   #14
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Re: No Raw Water Flow To The Generator

Quote:
Originally Posted by enjaku View Post
I have a Paguro 4000 generator onboard that is not getting any raw water flow.
1. The sea cock is open
2. I can blow air through the intake hose at the strainer and hear air escaping underneath the boat.
3. If I remove the impeller and cover, I can blow air from from the strainer through to the pump, so I know the hoses are clear.
4. The strainer is clean
5. I replaced the impeller twice with the same affect. The impeller appears to be seated properly and is undamaged.

I do not see any raw water in the strainer when the generator is running, and the generator soon shuts down as it starts to over-heat.

Any thoughts?
Common problem
Usually air in the system. Cause could be several. If you can blow through the system out you either don't have a non return valve or it is installed in the wrong position ( flow out) . If you don't have a non return valve I recommend to install one as close to the pump discharge as possible. This will keep the system flooded when you shut off the generator and you will not have air in the system once it is primed.
One other cause could be wrong rotation of the pump. Happen when the pump is disconnected and re connected sometimes.
I have installed a bleeding valve before my generator to purge any air out of the system.
Good luck
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Old 13-05-2016, 11:03   #15
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Re: No Raw Water Flow To The Generator

Quote:
Originally Posted by enjaku View Post
I have a Paguro 4000 generator onboard that is not getting any raw water flow.
1. The sea cock is open
2. I can blow air through the intake hose at the strainer and hear air escaping underneath the boat.
3. If I remove the impeller and cover, I can blow air from from the strainer through to the pump, so I know the hoses are clear.
4. The strainer is clean
5. I replaced the impeller twice with the same affect. The impeller appears to be seated properly and is undamaged.

I do not see any raw water in the strainer when the generator is running, and the generator soon shuts down as it starts to over-heat.

Any thoughts?
We T [with valve] our raw water wash down pump into both the engine and generator raw water intake circuits for two reasons: to prime those circuits, and to act as back-up should the primary raw water pump fail. [The strategy being that even in worse case- if impeller blades are stuck in the coolant channels- some water is better than no water...]

On our generator, we eliminated the water pump [and the belt that drives that and the alternator] in favor of a March pump. We don't need either function built into the generator as the March pump and main battery charger both run when the gen does.

Good luck resolving what can be a time consuming issue...

Cheers!

Bill
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