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Old 26-02-2012, 03:07   #16
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Got my new ones from onan factory in Melbourne and the have been great since 160 hrs. Dont know what was in it before.
The pump from memory has 3 screws to remove the side plate?
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Old 26-02-2012, 03:20   #17
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Re: ONAN Genset Raw Water Impeller Failure

There's something in the memory banks about failures between swapping Jabsco and Johnson, the impellors had longevity issues, looked the same but did not substitute well, just wondering if similar issue? Although totally agree on the running dry issue BUT why isn't every one having same issue????
I'd look long at the question of substitution as most problems occur after long laydown times where impellor deforms or wrong impellor type.....
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Old 26-02-2012, 03:42   #18
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Re: ONAN Genset Raw Water Impeller Failure

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Originally Posted by impi View Post
I have also been advised to remove the 'cooler' and clean it out as the broken rubber fins get trapped in the housing causing heat build up.
You can remove the end caps without removing the cooler...then use a wet/dry shop vac to suck out all of the impeller blades...2 or 3 blades will almost certainly cause yo a problem as this is a small cooler.

One other thing that no one has mentioned: This model pump has a key on the shaft which aligns to a slot on the impeller. These keys wear and the impeller will spin on the shaft...check the key.

I have a MDKAV 7.5kw 230 volt model and keep a spare pump as well as spare end caps and impellers.

Glad to read about the metal pipe electrolysis...I have replaced that once.

Bill
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Old 26-02-2012, 03:48   #19
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Re: ONAN Genset Raw Water Impeller Failure

Yes that electrolysis is very real... Slip a wire between each clamped hose so everything is common.... Air leaks on the suction side will also give you crap..... Frank
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Old 26-02-2012, 04:18   #20
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Re: ONAN Genset Raw Water Impeller Failure

Also if you've got a leak at any point above the waterline in the pipe,connections or raw water filter you'll drop suction/introduce air and damage the impeller a little more each time on start up.
I realise i'm stating the bleeding obvious but sometimes..........
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Old 15-11-2012, 09:52   #21
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Re: ONAN Genset Raw Water Impeller Failure

FYI.

The Antares 44i Catamarans use a 120V pump to fix this issue. Antares does not mention the brand of the Aux. Water Pump.

You can see the video of the generator setup here: http://www.liveantares.com/videosTech.htm

The electrical connection diagrams are in the Catamaran Owner's Manual: Antares Yachts - Manuals

Search for "Water Pump" in the manual.

It seems that the pump used in Antares 44i is the March LC-3CP-MD Pump, West Marine number 493973 (MARCH PUMPS Airconditi at West Marine), which is a seawater circulation pump.

Amazon.com has the March LC-3CP-MD Pump for $233 plus $12 shipping (March Pump LC-3CP-MD 115V: Amazon.com: Industrial & Scientific)

I know this is an older thread but I hope this helps...
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Old 18-11-2012, 22:54   #22
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Re: ONAN Genset Raw Water Impeller Failure

OOPS ... missed this reply a while ago ... we actually changed out the pump and installed an air conditioning style pump ... it works GREAT and so far have not spent another thought on these stupid impellers. They are not Johnson ... name somehow has slipped my mind!
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Old 18-11-2012, 22:55   #23
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Re: ONAN Genset Raw Water Impeller Failure

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Yes that electrolysis is very real... Slip a wire between each clamped hose so everything is common.... Air leaks on the suction side will also give you crap..... Frank
HUH ??? would like to know more about this ...
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Old 19-11-2012, 00:06   #24
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Re: ONAN Genset Raw Water Impeller Failure

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HUH ??? would like to know more about this ...
Years ago i installed a wet exhaust on our mono, i welded up SS bends to take the exhaust from the 4108 Perkins to the transom using steam hose (rubber) in between.

I hose clamped the hose to the stainless tube.

I injected seawater into the exhaust system to keep all cool. It worked beautifully the flexing hose absorbing the noise along with the water muffling it. I had no commercial water lift nor muffler fitted.

About 18 months down the track i had to remove it all to fit a new freezer in, when i undid the hose clamps the SS tubing was corroded directly under the clamps.

Now this was a steel round bilge boat and from the hull to the engine there were three SS tubing components. The problem is a current flows through such things and if these things are not common to each other then there is a risk of sacrificial corrosion same as an anode.

I rebuilt the fittings and upon assembly i placed a SS strip 10mmx.5mm between the rubber and hose clamping it in place with the hose clamps, so effectively every element was bonded to each other the hull and the engine.

20 YEARS LATER still no corrosion.

Under USL Code for commercial vessels in survey all piping that has a rubber interconnection must be electrically bonded to prevent sacrificial corrosion between.

Although the pundits will criticise with their own hypothesis facts are facts our corrosion simply ceased.

Cheers
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Old 08-01-2013, 05:43   #25
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I have just replaced an impellor and got a blockage out of the heat exchanger.

The genset will run for 10 minutes and then stop with a fault of no raw water flow.
The water is flowing really well after clearing out salt cake type stuff but the fault comes up no raw water flow?
Any suggestions?
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Old 03-11-2013, 18:27   #26
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What was the blockage. I had similar problems - head was chocked full of a jelly type substance - eventually put down to reaction if a silicate based coolant with another type. There is a bit written about it - I posted something a few months ago. Head came off and blasted through and Ok (well at least the overheating bit - I still have other issues with it).
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Old 04-11-2013, 00:33   #27
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Mostly bits of rubber impellor fingers pumped down the pipe and into the exchange unit.
Cleaned them out and some scale and now it flows great.
The raw water sensor is faulty so i have taken a wire off it so the genset will run.
Best i get a new one.
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Old 30-11-2013, 15:22   #28
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Re: ONAN Genset Raw Water Impeller Failure

I have a 2012 model Sanya fitted with a 7.5kva Onan, I have done 886hrs, I have already been through three impellers, the first time a found a small bit of sea grass and put it down to that, but once I replaced that the second one went within two months, I run the gen 3hrs a day, the next time it was a month and it went again, a month and a half later it had started to break down again.

I tried different suppliers due to old stock ect.
After the first time I had such a problem getting all the pieces from the heat exchanger and I know I got them all as put the old one back together like a jigsaw.

After that I placed a sea strainer in the rubber tubing from the raw water pump to the heat exchanger, this has worked really well, as I do regular checks and pick up straight away if the impeller is coming apart as I can see the little bits in the glass strainer, it is also good as the impeller is not run until a complete failure before you know there is a problem.
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Old 30-11-2013, 16:29   #29
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Re: ONAN Genset Raw Water Impeller Failure

I have a Sanya 2012 model with Onan 7.5 KVA.
I have had the same issues just replaced the 4th impeller, it has done 886hrs, so not happy.

I tried impellers brought at different locations in case they have been sitting to long and gone brittle, still no luck.
After spending 3hrs in very cramped conditions I placed a inline sea water strainer to collect the broken off impeller blades instead of them traveling to the heat exchanger. I had to place the old one together with the broken off bits like a jigsaw puzzle, just to make sure nothing was blocking the heat exchanger.

I just change out the impeller and it took from getting my tools ready, going done in the dark to engine bay, working with touch I replaced the impeller and checked the sea water strainer plus the new strainer I place between the raw water outlet and the exchanger.
Packed my tools returned then to there stowage and washed my hands, total time 27 minutes.

I would like to know why they are not lasting 500 hrs like the book said?
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Old 30-11-2013, 20:42   #30
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Sea strainer is a great idea.
Any particular brand that you have used,going to install one asap
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