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Old 06-14-2015, 08:09 AM   #1
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Generator raw water pump

So, two weeks ago, I neglected to open the sea cock while firing my 10 kw generator, and wiped out the impeller. Not the end of the world , and ordered another to keep up my spares.

Yesterday I fired up the generator to realize it was not pumping water. Checking all lines for blockag and verify water at pump, re fire, and still no flow. Off with the impeller cover only to see the impeller looks pristine. Re fire, and still no flow, it is then I happen to notice some run out on the pump pully. Looking down at the pully, I'm now wondering how could the key have failed especially with the set screw I'm looking at. Removing the pully I find the shaft is has a keyway, but the pully does not, and is retained by a set screw.

This is a Jabsco pump.

How many have this set up, and is this common for our type of generators?

There's no idler to adjust the pully, and I can see how this set up makes it easy to get a belt on. I really don't like this unreliable design, and for sure don't like the fact my pump shaft is now scored. I'm thinking of replacing the pully with a keyed pully. Now that the pump shaft is scored, and the shaft keyway is also buggered, fit up is going to be less than ideal.

Conall
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Old 06-14-2015, 08:57 AM   #2
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Generator raw water pump

I just replaced my impeller prior to launching. On mine the two mounting bolts had short slots (about 1/4" long) to slide the pump to tighten the belt. I actually found it easier to use the 'wobble' with the loose bolts more beneficial to getting the belt on than the slots and sliding the pump.

While I had the pump off I replaced the shaft seal. There was a very small leak when running it.

I wonder if your system is airbound because you ran it dry?? Can you use a hose and open up the strainer and push water into the system as its running? To assist the jabsco pump to ensure no airblock. Then once you have flow seal up the strainer. Years ago I did this on a stubborn generator and removed the impeller to get the air out. Then once I got flow I reinstalled the impeller.

Regarding the belt, Mine uses a toothed belt that depends more on the teeth than the tension
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Old 06-14-2015, 09:34 AM   #3
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Cappy,

I didn't describe things well enough.The set screw holding the pully to the shaft came loose and the pully was slipping on the pump shaft. I re installed the pully, tightened the set screw, and its pumping fine. The set screw design is too unreliable for me.

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Old 06-14-2015, 12:46 PM   #4
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Agreed, get a keyed pulley. Clean the shaft with a fine flat bastard file, it will be ok, just clean it dont reduce it.
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Old 06-14-2015, 04:02 PM   #5
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Get a shop to keyway broach the pulley you have. Then again, it might be just as cheap to buy a new one!
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Old 06-14-2015, 07:48 PM   #6
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There is nothing wrong with the set up as is. Just clean the threaded hole and set screw, and then use thread locker on the set screw. If the hole is deep enough you can add a second set screw on top of the first to lock down it down if you feel the need for a belt with your suspenders.
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Old 06-14-2015, 10:21 PM   #7
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Also, in addition to threadloc, make sure you are using the set screw with w beveled point, not the round cup point. The bevel point will sit INTO the keyway. A setscrew with w crown will just mash down the edges.
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Old 06-15-2015, 06:16 AM   #8
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The set screw bore is deep enough for a lock screw. I'd feel comfortable with this set up. Thanks all.

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