Need an Oman 8.0 kilowatt genset water pump

[BobBarr]

I'm trying to find an Oman 8.0 genset impeller pump for my hunter passage 42
With out much luck
Oman wants 730.00 for s new one..... anyone have any ideas?
Thanks.....

 

[Rick486]

Is it a Johnson pump? If not, I would imagine it is an out sourced pump from a third party. Onan is not in the pump business.

 

[Terry Cox]

impeller pump

Hi Bob, the sea water pump, right? What is wrong with the old one? These are pretty sturdy units.

 

[BobBarr]

Is it a Johnson pump? If not, I would imagine it is an out sourced pump from a third party. Onan is not in the pump business.

Im told its an Oberdorfer but I found a Sherwood that looks exactly like mine on Ebay at much less money.......any thoughts?

 

[BobBarr]

Hi Bob, the sea water pump, right? What is wrong with the old one? These are pretty sturdy units.

Hi Terry..........yes its the sea water pump........i had a master craft mechanic on the boat for 5 hours trying to ascertain the problem..........Im not getting water out of the side of my boat and the generator shuts down before it overheats......the mechanic checked the thru hull and the hoses from the bottom of the boat up to the strainer and from the strainer to the pump and no water or suction is drawing into the pump..........he changed the gasket....no luck.....when he put in a brand new impeller and still no suction coming into the pump he told me it had to be the shaft not rotating and a seal must be broken in the back of the pump...........im not very savvy when it comes to these things so if you have any ideas for me I would really appreciate it as the pump is really expensive.....anything else you can think it might be Terry.........? thanks so much

 

[BobBarr]

Im told its an Oberdorfer but I found a Sherwood that looks exactly like mine on Ebay at much less money.......any thoughts?

the pump on the right is my pump the pump on the left is the Sherwood I found on Ebay at a lot less money than from Onan........any thoughts..Im at a loss as to what to do........

 

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[Rick D]

Is this the one you found on e-bay? http://marineenginedirect.com/oberd...mqjMXTAuetKaswu6-oFnxCHTXnP928wwaAlksEALw_wcB It does list the model it applies to. Here is the one for an Oberdorfer: http://marineenginedirect.com/oberd...KmqjMXTAuetKaswu6-oFnxCHTXnP928wwaAlksEALw_wc Finally, here is the answer: http://www.pumpvendor.com/Sherwood_G905_G-905.html Of course, the best way is to take it off (or have it taken off) to verify before ordering, but I agree that it looks the same as what is in your photo. And, replacing the pump would appear to be the right thing to do.
BTW, I would get another impeller and gaskets if your decision is to buy that new-old stock. The impeller could be bad from sitting in that position a long time IMHO. Good luck!

 

[Terry Cox]

Hi Bob, sheesh, at a loss here. The only two times the Onan shut itself down was when there was no coolant sea water being drawn in by the pump because:

1. Failed to place the sea water strainer cover on properly after cleaning the basket, so the unit sucked air past the seal preventing sea water from being drawn in by the pump, which caused it to shut down.

2. Sea water strainer sucked in a pile of marine gunk in a very dirty bay, clogged the strainer and caused the unit to shut itself down. During the trouble shooting process I did replace the badly worn original impeller. The unit has run normally ever since, and that was maybe 25 hours ago.

Beyond that not of much help here. Does the pump impeller drive shaft rotate when you turn the engine over? Be sure the sea water strainer cover is on and sealed tight. If so, you should be able to siphon in water to the pump. I'm not aware of a shaft seal that would prevent the pump impeller from drawing in sea water. These units are pretty simple in design. Perhaps a rebuild kit rather than a new unit? Just say'n.

If you can talk to Onan technical support, give them the symptoms and see what they say. Drill into possible scenarios with the support person before buying a new unit.

 

[LeslieTroyer]

I'd find a new mechanic. There are several things besides the shaft that will cause loss of suction
1) is the gasket the correct size, to thick no prime
2) is the cover groves or warn. Flatten with wet dry paper on glass.
3) scoring/worn pump housing.

To see if it is the shaft. With pump cover off bump the engine. Does the shaft turn???


Good luck
Les

 

[Terry Cox]

1) is the gasket the correct size, to thick no prime

Good suggestion, Les. Our pump cover gasket is pretty thin. Bob needs to make sure the mechanic removed the old gasket did not install another gasket over the old one.

 

[LeslieTroyer]

Mine is thinner than standard printer paper

 

[BobBarr]

Is this the one you found on e-bay? http://marineenginedirect.com/oberd...mqjMXTAuetKaswu6-oFnxCHTXnP928wwaAlksEALw_wcB It does list the model it applies to. Here is the one for an Oberdorfer: http://marineenginedirect.com/oberd...KmqjMXTAuetKaswu6-oFnxCHTXnP928wwaAlksEALw_wc Finally, here is the answer: http://www.pumpvendor.com/Sherwood_G905_G-905.html Of course, the best way is to take it off (or have it taken off) to verify before ordering, but I agree that it looks the same as what is in your photo. And, replacing the pump would appear to be the right thing to do.
BTW, I would get another impeller and gaskets if your decision is to buy that new-old stock. The impeller could be bad from sitting in that position a long time IMHO. Good luck!

Hi Rick,
Thank you so much for this excellent information.........the price for the oberdorfer that you found was 40.00 less than the same pump I was quoted from Depco......which is where oberdorfer rep sent me................my only concern is that I havent exhausted every other possibility before I spend 300.00 on the pump, pay to have it installed and still not have water run through the generator and out the discharge port into the lake......Im just torn as to what to do next........but your thoughful and intelligent advice is greatly appreciated as is all the kind sailors who took the time to provide advice to me regarding this situation.

 

[BobBarr]

Hi Bob, sheesh, at a loss here. The only two times the Onan shut itself down was when there was no coolant sea water being drawn in by the pump because:

1. Failed to place the sea water strainer cover on properly after cleaning the basket, so the unit sucked air past the seal preventing sea water from being drawn in by the pump, which caused it to shut down.

2. Sea water strainer sucked in a pile of marine gunk in a very dirty bay, clogged the strainer and caused the unit to shut itself down. During the trouble shooting process I did replace the badly worn original impeller. The unit has run normally ever since, and that was maybe 25 hours ago.

Beyond that not of much help here. Does the pump impeller drive shaft rotate when you turn the engine over? Be sure the sea water strainer cover is on and sealed tight. If so, you should be able to siphon in water to the pump. I'm not aware of a shaft seal that would prevent the pump impeller from drawing in sea water. These units are pretty simple in design. Perhaps a rebuild kit rather than a new unit? Just say'n.

If you can talk to Onan technical support, give them the symptoms and see what they say. Drill into possible scenarios with the support person before buying a new unit.

Hi Terry...........thanks for your sage advice......we tested both scenerios you mentioned and neither seemed to be the problem.......we had water from the thru hull up into the sea strainer and then the problem starts as I cant feel any suction in the intake port on the water pump but the impeller is new and turns on the shaft........my genset has a heat exchanger......do you think that could be the problem if the heat exchanger is clogged with some kind of muck?......Im just trying to explore all possible avenues before spending the money on a new pump.........but I dont know what to do next.......thanks to all of the help I received here from you good people at least I know where to get the pump if that proves to be the problem.........thanks again to all for your help on this problem.

 

[BobBarr]

Thanks Les..........I will check on the gasket situation..thats a good idea........the mechanic I hired put in a new gasket,I believe, when he replaced the impeller, but i will check it out.........im really confused as to what to do before spending the money for a new pump and still risk the problem to not be solved.........I really aprreciate everyones great advice on this................

 

[BobBarr]

Thank you Les for this great advice.......if it turns out to be one (or two) of the possible problems you have identified will I need a new pump to correct these items........forgive my ignorance but I do not know what "wet dry paper on glass" means..........are you saying I might be able to correct these items without purchasing a new pump?.......thanks again for this great advice.........

 

[LeslieTroyer]

You can fix a groved cover by using wet/dry sandpaper (wet) laying on a piece of glass. The glass is to make sure the cover stays flat. Depending on depth of groving start with 220 and once it's flat use 440 till big scratches are gone then 600 until the 440 scratches are gone. Keeping the paper wet the whole time keeps the paper from clogging and gives a better finish. Starting with too fine a paper will just make the process take longer. Or take the cover to a machine shop for flattening it should cost ~$20

The gasket between the pump and cover is about half the thickness of printer paper. If not a new thin gasket is required

Only a scored pump would have me looking for a new pump. (Under $300 ) if you look aroundd

 

[BobBarr]

Once again Les....thank you so much for your sage advice and instructions.........this area is not my strong suit and Im a bit lost here so I am very appreciative of your assistance.........could the problem lie elsewhere other than the pump? we checked all the clogging possibilities in the hoses that lead up to the impeller and found no blockage.......is there a way to check the discharge hose to see if it possibly collapsed or could it be getting stuck in the heat exchanger?............thanks

 

[LeslieTroyer]

To check for obstructions past the pump you could pull the pump outlet hose and put a female garden hose repair piece there and hook up to a garden hose. WARNING 1) do not turn your hose on full just above a trickle. Check for water at exhaust. 2) if you have wet exhaust first disconnect hose going to the exhaust mixing elbow and put it in a bucket (you don't want to flood your engine with water)

After the pump you don't usually worry about hoses collapsing, the water pressure will keep them full. Hose kinking could happen but this thing probably hasent been moved so again not likely, but "easy" to check.

 

[1mcarlson]

Bob,
Are you currently in East Chicago on the hard?
Who did you have look at your pump?


Mike Carlson
91 Hunter 42 Passage
Hammond, In.