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1978 6 hp Evinrude 6804b Water pump rebuild, help needed!

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  • 1978 6 hp Evinrude 6804b Water pump rebuild, help needed!

    Hey everyone,

    I recently purchased a 1978 Evinrude 6804b. I pulled apart the water pump to replace the impeller because it didn't seem to be moving much water and what it was moving was pretty dang warm out the tattle tale. (The guy I bought the motor from said to worry if the water was steaming)

    I have some questions as to whether or not I should be replacing more than just the impeller. The impeller looks fine visually, but there is some obvious wear to the impeller plate. Should it be replaced?



    Also I believe it still has the older style housing. From what I have read, the new ones with stainless steel insert for the impeller are better. This is what is on it currently.



    Am I better off to just order a complete water pump kit, or should I just replace the impeller and the impeller plate?

    Thanks for your help!
    Last edited by 08trdoffroad; August 15th, 2013, 07:42 AM.

  • #2
    Re: 1978 6 hp Evinrude 6804b Water pump rebuild, help needed!

    That housing looks worn out to me. If it were me, I'd install the new style pump and be done with it. Part number was 391391, now changed to 763758.

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    • #3
      Re: 1978 6 hp Evinrude 6804b Water pump rebuild, help needed!

      Ok, that is what I suspected. Where is the cheapest place to pick up the kit online along with a new drive shaft pin. The one I pulled out was on it's last leg.

      What is the best method(Solvent) of cleaning things up before I reassemble?
      Last edited by 08trdoffroad; August 15th, 2013, 09:11 AM.

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      • #4
        Re: 1978 6 hp Evinrude 6804b Water pump rebuild, help needed!

        I have the kit and pin on order.

        What is the best way to go about cleaning up the internals, everything has a pretty thick layer of carbon on it.
        Last edited by 08trdoffroad; August 15th, 2013, 11:38 AM.

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        • #5
          Re: 1978 6 hp Evinrude 6804b Water pump rebuild, help needed!

          i would clean old housing, this samll bleed hole and clean spece under gromet

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          • #6
            Re: 1978 6 hp Evinrude 6804b Water pump rebuild, help needed!

            While running the motor yesterday in the garbage can after rebuilding the fuel pump I noticed something that I would like some input on, I replaced the impeller and water pump assembly about a month ago. The motor only has about eight hours on the new impeller. I noticed with the motor running yesterday, the water coming out the tale tell was steaming. I have read the water can be pretty warm coming out it, but should never be steaming hot. Pay particular attention to about 0:20-:030 in the video and you can see it.

            Could it possibly be that the ambient air temp when I was running the motor was only 50-55 degrees?

            Anyway, here is the video of the motor running!

            1978 6 hp Evinrude Outboard running after fuel pump rebuild - YouTube
            Last edited by 08trdoffroad; October 9th, 2013, 09:33 AM.

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            • #7
              Re: 1978 6 hp Evinrude 6804b Water pump rebuild, help needed!

              Yikes !! The impeller work should be looked at. It should be no trouble to drop the lower unit and check that you have everything fitted. Things like the impeller "tab" (that locks it to the drive shaft) is in place, and the end (splined end) that fits into the powerhead is greased. The powerhead end is not the problem, but the Tab end is. I'm sure you'll find the problem....
              Light travels faster than sound. This is why some people appear bright until you hear them speak.

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              • #8
                Re: 1978 6 hp Evinrude 6804b Water pump rebuild, help needed!

                So in your opinion the motor is running too warm? I am going to be pretty frustrated if the motor has shredded the new impeller already!

                I will drop the lower end and check it out. I didn't notice this issue when I had it out on the lake last weekend, just when I ran it in the garabage can for a few minutes yesterday to make sure the fuel pump was functioning correctly after the rebuild.

                If the impeller is damaged, should I grease the new one with anything? (if it isn't should I still grease it with something?) I say a youtube video where the guy put something on his...

                What type of grease do you recommend for the splined end that inserts into the power head?
                Last edited by 08trdoffroad; October 9th, 2013, 10:28 AM.

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                • #9
                  Re: 1978 6 hp Evinrude 6804b Water pump rebuild, help needed!

                  No, I don't think you damaged it , there is same water being pumped , perhaps from the friction of the impeller to the drive shaft. I watched to video again to see that you had enough water covering the the pump ( should be 2-3 inches ABOVE ) the pump, it looks like you did.

                  When you assemble pump, place impeller on drive shaft, fit onto Tab, then place pump top, down shaft until it makes contact with impeller. Th trick to getting ALL the water vanes of the impeller turned the right way is to turn the pump top COUNTER-CLOCKWISE , thats right , turn the opposite direction....then to final position when fully seated. You can put some dish washing soap in the pump housing to make things easier.
                  Last edited by Xcusme; October 9th, 2013, 10:43 AM.
                  Light travels faster than sound. This is why some people appear bright until you hear them speak.

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                  • #10
                    Re: 1978 6 hp Evinrude 6804b Water pump rebuild, help needed!

                    OK! I will check to make sure everything is in place as it should be and report back with my findings! Thanks for your help!

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                    • #11
                      Re: 1978 6 hp Evinrude 6804b Water pump rebuild, help needed!

                      make sure you only turn the shaft clockwise. The impeller can become damaged if you turn it the other way. I have taken a part a few that had fins pointing in two different directions. Did you replace the housing? If not them you should
                      The outboard guy......

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                      • #12
                        Re: 1978 6 hp Evinrude 6804b Water pump rebuild, help needed!

                        I did replace the housing. It now has the newer style with stainless steel insert.

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                        • #13
                          Re: 1978 6 hp Evinrude 6804b Water pump rebuild, help needed!

                          I pulled the lower unit. Nothing appeared out of the ordinary. All components were in place as they should be. No damage to the impeller...I'm at a lose as to why the water at the tale tell was steaming...

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                          • #14
                            Re: 1978 6 hp Evinrude 6804b Water pump rebuild, help needed!

                            Well, it will take a short while to sort things out, but if your willing to do some simple tests, things will be right. The next thing, is to test the tube that carries the water up the lower leg. There is a small gasket , at the top of the pipe, that seals it. On some motors if this gasket gets overheated (from a worn impeller) it will be mis-shapened and block the water flow. It would be nice if this water tube just pulled out but if memory serves, you'll have to drop the power head. Now, before you do that (it;s not that hard) next try pulling the thermostat. It's just 3 screws at the rear of the power head. Next , try and put water up the cooling tube. This will take an adapter that is available from the hardware store. It reduces a water hose down to the size of the water tube. If water doesn't come up to the thermostat housing , it the small gasket , and you'll have to remove the power head to fix it.

                            It will take a few small steps to determine your problem....I hope the steps are small. Let us know what you find.
                            Light travels faster than sound. This is why some people appear bright until you hear them speak.

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                            • #15
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                              Re: 1978 6 hp Evinrude 6804b Water pump rebuild, help needed!

                              When I replaced the impeller and housing a month or so ago, the gasket you mentioned was misshapen. I replaced it as a new one came with the water pump rebuild kit. I wonder if it is possible that the motor sucked up some debri into the water system when I was on the lake. I did notice there was quite a bit of algae pieces in the water...

                              What should I be looking for when I pull the thermostat? Do you have a link to the adapter you are talking about?

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