8kw onan gen

[hatterass]

I have a 8 Kw genset on my boat that I don't use all that much. Went to winterize it the other day and no water came out. thought it was the impeller. changed that.. still no water? checked the seacock open and working. what gives? could the impeller shaft be broken? it's driven off the motor.
thanks Dave
PS I checked for clogged lines, none.

 

[34Hatt]

Hey Dave

I have the same one it could be the shaft or some thing clogged, air leak!!
Try cranking it one shot with the cover off and see if the Impellar turns! If so try another hose and a bucket to see if it will pull water.
Good luck Dan

 

[hatterass]

Thanks Dan,
I thought someone was going to suggest that. you know what a PITA it is to get the cover off. Is it possible for the shaft to be broken? when I changed the impeller I checked to see if it was ok felt fine. I do have water coming right up to the impeller from the raw water side, that should be enough to get the water pumping right?
Thanks Dave

 

[david_lavigne2540]

I found on the A/C water pump that they left off a o-ring which caused it to leak a little air. This caused it to not pump water Up the hose through the A/C and back out.

Could be that your seal isn't tight. But that's a guess.

Turn the fuel off
Turn the water off
Have somebody crank the engine while the implellor cover is off.
If the implellor spins, then you know the spindal is good.

I don't think it would hurt the engine to run for about a minute or so without the implellor connected. But I'm not certain, not a mechanic.

I would disconnect the Hose leading out of the impellor and connect it to another hose that is just above the engine height leading to the bilge area. It should be able to pump water while running for a minute into the bilge area.

Or do the bucket trick from the Phosporus cleaning tip. You can see the water circulating in the bucket, Picking up water, and putting it back in the bucket. I wouldn't run the generator long, or the bucket might melt if it's plastic, or melt through the hull if melt. (laughs)

 

[Will]

If it's a Jabsco type pump, sometimes the splines go bad on the impellor and it fails to turn. The splines on the shaft can go bad too but that is less likely since the shafts are stainless and the impellor splines are brass.
Will

 

[34Hatt]

Yeah dave that cover is in there I did mine on a bench before I put it in last year after repower not looking foward to next one. But If you do it you'll have your answer! That water level is close because it is sitting low in the boat so it should pick up prime right away.
Dan

 

[67hat34c]

warn impellor and or warn housing will also cause this. I changed the impellor on mine this year and when i reinstalled the back of the housing , did not put back in exact position as it was before and the thing would never hook up. wound up rebuilding the pump with new shaft, impellor,wear plate and the rear housing, now it pumps like never before. cant have any cavitation in the pump or it wont pump water.

 

[ednolan]

These pumps occasionaly loose their prime. Close the sea cock, remove the inlet hose from the pump and fill it with water, start the generator and immediately open the seacock and look at the gen. exhaust for water flow.

 

[REBrueckner]

If you don't want to remove the pump cover for testing, remove the intake hose at the pump and be sure there is raw water water to the pump. Then remove the discharge hose from the genny, put it in a pail and run the genny..BRIEFLY!!!! Just a few seconds....

If water is coming out the discharge hose, likely the downstream hoses/heat exchanger is clogged. If no water comes out, you'll know it's the pump/impeller.

You might well find a clogged hose/fitting..perhaps an impeller piece, maybe a piece of hose...

 

[hatterass]

I'm not getting anything on the output side of the pump. I have water right up to the pump. the old impeller was fine. I did notice that the sea strainer was leaking from the bottom a little bit but, when I turn it on the water flows freely. I think I am going to have to take the cover off again.

 

[Banshee36]

check for grass in the strainer or the hose from the seacock to the strainer. Mine shut off this summer and eel grass was the culprit.
JW

 

[REBrueckner]

haterass..based on your findings something in/at the pump itself is at fault...depending on type, check to see if the drive shaft turns the impeller (turn the genny via the starter) and also check the cam....did you check the pump inlet and outlet for clogging..maybe grass on the intake or an impeller piece in the discharge....look inside with a flashlight!!!!

 

[hatterass]

Yup, No grass and the hoses were clean. new impeller and water right up to the pump. sounds like I have to take the cover off and more then likely rip apart 1/2 the motor just to get the pump of and replace. Well at least there is all winter.

 

[REBrueckner]

Before you do all that, check the pump inlet and outlet connections for obstructions with a flashlight....

 

[hatterass]

Yup, did that to when I had it apart just for good measure. all clean. this sounds like it is getting expensive as well as hard on my back. I have been hunched over for a week now from working on it. And I'm only 32!
I think I am getting old?

 

[rjwilliams11741]

Before you start tearing the pump apart pull the hose off the outlet side of your heat exchanger at the connection to the exaust elbow. If you have water to there then you probably have a problem with the mixing / exaust elbow. Then try pulling the exaust pipe off the elbow and see it you get any water. I've had both my 15K and 7.5 K elbows clog up at the water intake.

With a bit ingenuity you have build a new one with a galvanized nipple, a galvanized "T". It will take some welding but sure beats Onan's prices.

 

[hatterass]

I did that to. there was no water coming out. just exhaust. I has to be something with the pump

 

[67hat34c]

I just went through this with my MCCK. has the same raw water pump i believe.
i put in a new impellor and the thing would not pump. turns out there was a wear pattern on the inside of the rear housing. it was warn out and the pump would only cavitate.

take it apart and you will see what i mean. the wear plate will have what appears to be a symetrical groove in it, that is not factory just wear. the rear impellor housing will also have wear in the back of it. it needs good seal where the veins rub on the front, back and the leading edges otherwise it will cavitate.

You need pump kit with a rear housing and all will be well.

 

[hatterass]

I'll check that, I did notice that it was worn. that still does not explain why it would work on day and not the next. but cavitation is a good idea.

 

[REBrueckner]

Don't get discouraged....3/4 of the problem is usually finding out exactly what's wrong. Winter is the BEST time to determine root cause(s) and do some work...at least here in the NE it's nice and comfortable working with a little heat on rather than 80 or 90 summer temperatures.
This June, a month after I left for my six month summer cruise, I spent about three hours daily for four days trying to figure out why my 12KW Onan would start some days, not others. I did not have that problem in the prior year!!!!??

I'll post that story here next week or two when I get my log for accurate references, but it turned out to be a $3.00 part!!!