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90hp mercury water pump problem

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  • 90hp mercury water pump problem

    I have a 90 hp 1986 mercury outboard, it is not getting enough water to the engine. The impeller looks good, but the top housing seal seems to be gone, would this cause the pump to suck air and not pump water to the engine?


  • #2
    Re: 90hp mercury water pump problem

    Peg, You need to be a bit more specific. There is no seal in the water pump cover. There are gaskets that sandwich the impeller. There is a seal in the waterpump outlet, where the water tube fits.

    How do you know you are not getting enough water?

    Comment



    • #3
      Re: 90hp mercury water pump problem

      I have the lower unit off and I can see down through the water inlet groves. I am going to replaced the whole water pump unit to see if this helps with my problem. The water is not even coming out of the pee hole even when idling. Does the shaft that runs the impeller turn all the time?

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      • #4
        Re: 90hp mercury water pump problem

        I have taken an air hose and blown air through the line, air comes out at the bottom of the water pump inlet hose, but when I put my finger over the hose air comes out somewhere inside the housing. It seems I have a hole in my water hose going to the engine, or is this normal?

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        • #5
          Re: 90hp mercury water pump problem

          Peg, You have really confused me now. There is a single copper watertube the connects to the water pump cover and supplies the motor with cooling water.

          Just so you know, water from the lake enters the waterpump base from the bottom thru the 4 holes on each side of the geracase, just above the bullet shaped part of the gearcase. The impeller runs in a non-circular chamber, which causes it to be pumped up the water tube.

          The driveshaft is supposed to be splined to the impeller, so it turns whenever the motor is running.

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          • #6
            Re: 90hp mercury water pump problem

            I know all the mechanics of the water pump. I put air to the pee hole to check if there was an obstruction after I took the bottom end off.

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            • #7
              Re: 90hp mercury water pump problem

              Air don't mean Sh=t . Water does.

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              • #8
                Re: 90hp mercury water pump problem

                OK, that I understand. You realize the cooling system is an open one! Air blown into the telltale can exit thru the water tube or the exhaust extention. If you want to check for a cooling system obstruction, put a water hose on the water tube and give it a few pounds of water pressure. Just a little, or you may damage the powerhead. If you see water exiting the midsection, the water jacket is clear. Make sure the motor is vertical so the water doesn't get into the cylinders.

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                • #9
                  Re: 90hp mercury water pump problem

                  Thanks for the help, Chris 1956 I'll try the water hose to see what happens. Mi duck down if you don't have anything to comment for help I don't need your input.

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                  • #10
                    Re: 90hp mercury water pump problem

                    You do have the drive key between the driveshaft and the inpeller, right?

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                    • #11
                      Re: 90hp mercury water pump problem

                      Yes. Drive key is in. Hooked up water hose as you said. Water coming out of tube that goes to water pump. Put in new water pump today and all works good. Thanks for your help.

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