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Water Pump Question

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  • Water Pump Question

    The water pump repair kit, for my 1999 35Hp 3-cyl Johnson, arrived in the post today. But before ripping into, I'd like to pose a question here.

    When the outboard lower leg is submerged in a drum of water, the water pump works wonderfully. A nice strong water jet shoots from the outlet like a champ. All good.

    But when I try the muffs with garden hose trick, there is no water jet at all. Water supply pressure and volume is good. I have never seen this before and it has me stumped.

    Am I right to assume the pump repair kit must be installed?

  • #2
    In a barrel, test tank, whatever... the pump is submerged and is operating on its own as the pump has a continuous supply of water.

    On a flushette, the supply must be supplied to the pump with enough force to keep the pump fully supplied. You say the supply pressure and volume is good... perhaps not good enough? On the high hp models... usually thinking of say 40 or 50hp up... the water pressure must be turned on full force. The 35hp may be a border line hp as far as the full force water supply goes.... and if not enough, the exhaust pressure would be blowing it out the long exhaust housing quicker than the water pressure can fill the powerhead water passageways.

    However... and especially if you've been running that same water pump for a few years, I'd suggest you drop the lower unit so as to inspect it and at least replace the impeller rather than to chance ruining a days outing.


    • #3
      Good advice as always Joe!


      • #4
        While at the chandlery the other day, I purchased another set of mufflers. This set had smaller round ears, rather than the larger rectangular pair on me earlier purchase. This does the trick. I thought bigger would be better. But the larger rectangular ears were not a very conformal fit and must have let too much water escape so limiting the volume delivered to the pump.


        • #5
          Shows you're thinking..... Good for you. I still have both size flushettes myself (somewhere), probably cracked and rotted by now. It's been so long since I've used either one that I didn't give a thought to the two sizes in my original reply.


          • #6
            Just did my 1998 Johnson 3 cylinder 35hp for the first time last year. A couple things that might help to be aware of include:
            * My impeller was almost in perfect shape after all those years but it was the grommet that connects the pump output to the tube that had swelled dramatically and was leaking.
            * 2 of the gearcase extension bolts were pretty well seized. Took my sweet time and finally got them out ok but be aware there is not a lot of room to work there with the cavitation plate.
            * The shift rod disconnects under the water pickup screens. There are a couple small plastic V shaped sleeves/bushings that are slit/split so carefully peel them off. i damaged mine but was lucky enough to find a couple more (they were hard to find...).
            Otherwise it now works like a champ. Good luck.


            • #7
              Thanks Nauti. I have purchased a water pump overhaul kit as well as those keepers #0325625.