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4788 Cummins impeller replacement-gctid813981

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    4788 Cummins impeller replacement-gctid813981

    I'm having trouble getting the impeller out of my Sherwood pump. I tried using a puller but it won't move. I didn't want to pry on the pump and damage the seal surface so I stopped. Is there a trick too these? Thanks Dave

    Prior to getting impellers with a threaded hub to pull them out, I made a puller from a faucet handle puller. Small enough to fit between the vanes.

    The only other suggestion I have is to spray some diluted dish soap into the housing and flex each vane, then try to remove.


      I did see threads on tip of the impeller. Is there a special tool for removal?


        The original ones I have are threaded. I used a bolt to drive against the shaft and they came right out.

        That was last year, and my engines had 430 hours on them. No leaks.

        Now this year I noticed the starboard pump leaking around the shaft.

        Once I got over the unhapiness at cummins engineering for such a stupid location, it only took three or so hours to replace the pump with a Semax unit. Eliminated the fuel cooler at the same time.

        Fortunately I had a set of new pumps onboard in anticipation of this so it was a simple job to get after. Had to get a small bottle jack at NAPA but the whole thing was easier than I thought it would be.


        Whats the weather like on the boat

        Where am I right now?


          "dls" post=813984 wrote:
          I did see threads on tip of the impeller. Is there a special tool for removal?
          If the hub is threaded, a bolt will remove it. If my memory is correct, the bolt I use is a 1 inch diameter, 12 threads per inch. I use Sherwood 17000K impellers with the threaded hub.

          Check this to zoom in and see the threaded hub:


            Ron, it's not a 1" bolt, its more like 5/8" or 1/2", certainly lots of threads, so you're probably right with 12 per inch. I have one on the boat and will check in a few hours.

            Dave, I think it was Tony Athen who told me the best way was get some dish washing liquid in there, then crank it. Obviously not enough to start it, just a touch to kick it. Alternatively, a socket on one of the belt pulley will move it a tad. I've done that when I had to line up the key way. If the impeller is stuffed, I've used pliers and a pointed hook tool to pierce a vane and lever it out. It's in a bitch of a place with fuel cooler hoses close by. I also had to shorten the bolt to get it in the thread, but it got the impeller out far enough to get an "L" hook in and behind the vanes. But dish washing liquid and cranking it should break it free.

            Hope this helps. Cheers
            John H
            Brisbane QLD Aust

            2000 - 4788/Cummins 370's


              Thank you all for your tips.


                The bolt to remove an impeller is 3/4 - 16. This is not just for 4788s but for all the other 6B marine engines as well.
                1999 3788, Cummins 270 "Freedom"
                2013 Boston Whaler 130 SS
                Anacortes, WA
                Isla Verde, PR