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Alpha one Gen 1 raw water pump question.

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  • Alpha one Gen 1 raw water pump question.

    Hello,
    I have a 1990 Alpha one Gen 1 with raw water pump in the leg. I had this boat for 2 seasons. So last winter I bought all new parts for it. I didnt replace the pump this spring but did my thermostat. My boat ran 145F all of last summer. After replacing thermostat it ran about 150F? Kind of weird unless new thermostat was just a little different. I did get the 143 F thermostat. No overheating or anything like that last 2 seasons.

    Anyway so I serviced my drive today. I took everything apart and noticed the white water tube was melted like a mushroom. Everything else looked good. Impeller was little worn but not bad. Pump housing was decent and not melted. I replaced everything and checked it on the hose.
    My question is why was the plastic tube melted. Is this normal?
    I ran the boat for 2 seasons and never checked the pump. I also dont know the last time it was replaced. So does this happen over time. The big copper pipe was in good shape. Just the plastic one was melted on the top half. Also why did I get little variation in the temp after replacing the thermostat or was this because of a wearing pump.
    Thanks.


  • #2
    Re: Alpha one Gen 1 raw water pump question.

    Sounds like at some point the engine was run without water from the pump, and therefore no cooling water in the exhaust. The hot gasses melted the tube. Might be a good idea to take a look at the exhaust shutters, the hot exhaust probably didn't do them any good. 5 degrees, could very well be the variation in the thermostat, sounds like nothing to worry about. Good Luck.
    Terry
    87, 4WINNS H 190
    470/Alpha I

    Comment



    • #3
      Re: Alpha one Gen 1 raw water pump question.

      Thanks for the reply!
      What is the quickest way to check the shutters? I have 4.3 Mercruiser. When I ran the boat on the hose after pump service it got up to temp and ran at 145F. I think it will still go to 150F once warmed up in lake water. I will try to take it for a ride this or next week before I put her away. So this way I can check my drive after service and pump. Like I said I didnt do anything to the cooling system for 2 years. The only thing was a new thermostat this spring. Also how much are the shutters and how hard/easy is to replace them.
      Thanks.

      Comment



      • #4
        Re: Alpha one Gen 1 raw water pump question.

        ...not sure if you have the 4" elbow...but this will give you an idea.

        http://www.***********************/Me...ST%20ELBOW.pdf

        Remove pieces 1 thru 5 to get a peek at the shutter, Pc. 6.

        And, if the shutter is missing/damaged, look up into the prop to see if pieces are lodged in the foot of the lower unit. If the pieces aren't there, remove the complete drive and inspect the exhaust tube as it exits the transom.
        Eddie Petty. #3 Dirt Modified
        Courtland, Virginia
        V-20 Wellcraft
        3.7 470 Mercruiser

        Stumpnocker
        25 Yamaha, 25 Johnson, 25 Evinrude, 9.9 Evinrude, 4 Johnson, 2.5 Johnson

        Comment



        • #5
          Re: Alpha one Gen 1 raw water pump question.

          You can see the shutters in the upper exhaust by removing the rubber exhaust section and looking in the top of the y pipe. If your old shutters are missing look down in the bottom of the y, if they are in there it creates all kind of issues with back pressure and can allow damaging water back up the exhaust. If your old shutters have the rubberized edges burned off and there's just a metal edge they will rattle and jingle, water can get by them.
          The replacement parts are completely different looking. They are hard plastic with silicon rubber edges, they pop in to the pivot holes in the upper Y pipe. I think they are $12 or 18$ each.
          My boat has a 160 degree t-stat, and that's where it runs unless it is running really slowly. Example this past weekend I had it out on a cool day and the idle went down to around 500 RPM where it is supposed to be at 650. After a few minutes of no wake zone and other idling I looked down and saw 180. I brought up the rpms to 650 and the temp started down within seconds. In 100 yards at 650 rpm I was back to 160.
          PS I melted that same tube last spring, my first year with an Alpha.
          1989 Baja Sunsport 196, Mercruiser 5.7, Alpha 1
          Moultonborough Neck, Lake Winnipesaukee, NH

          Comment



          • #6
            Re: Alpha one Gen 1 raw water pump question.

            You can see the shutters in the upper exhaust by removing the rubber exhaust section and looking in the top of the y pipe. If your old shutters are missing look down in the bottom of the y, if they are in there it creates all kind of issues with back pressure and can allow damaging water back up the exhaust. If your old shutters have the rubberized edges burned off and there's just a metal edge they will rattle and jingle, water can get by them.
            The replacement parts are completely different looking. They are hard plastic with silicon rubber edges, they pop in to the pivot holes in the upper Y pipe. I think they are $12 or 18$ each.
            My boat has a 160 degree t-stat, and that's where it runs unless it is running really slowly. Example this past weekend I had it out on a cool day and the idle went down to around 500 RPM where it is supposed to be at 650. After a few minutes of no wake zone and other idling I looked down and saw 180. I brought up the rpms to 650 and the temp started down within seconds. In 100 yards at 650 rpm I was back to 160.
            PS I melted that same tube last spring, my first year with an Alpha.
            Whoops, Eddie beat me to it.
            1989 Baja Sunsport 196, Mercruiser 5.7, Alpha 1
            Moultonborough Neck, Lake Winnipesaukee, NH

            Comment



            • #7
              Re: Alpha one Gen 1 raw water pump question.

              Sounds good. I will check them out come spring. I really dont hear any noises coming from the engine. It runs always cool and 145-155F at idle or WOT. That tube freaked me out because I ran like that for 2 seasons but from I understand it's just a guide when putting everything together. So my number one guess would be a dry start done by owner before me.

              Comment



              • #8
                Re: Alpha one Gen 1 raw water pump question.

                Another question. When I had everything apart I took the copper pipe out to inspect the water box. Did I scew anything up? I just stuck it back in there and called it a day. I did run it on the hose after and everything looked normal. Also. I had 3 o-rings left over from my drive gasket kit and 2 gaskets from the pump kit.
                Do some alpha drives take more or different gaskets. I replaced all gaskets I took off so I didnt forget anything.

                Comment



                • #9
                  Re: Alpha one Gen 1 raw water pump question.

                  Originally posted by ccustomrides View Post
                  Another question. When I had everything apart I took the copper pipe out to inspect the water box. Did I scew anything up? I just stuck it back in there and called it a day. I did run it on the hose after and everything looked normal. Also. I had 3 o-rings left over from my drive gasket kit and 2 gaskets from the pump kit.
                  Do some alpha drives take more or different gaskets. I replaced all gaskets I took off so I didnt forget anything.
                  Really should be a new thread......

                  The excess o-rings were most likely from the top of the vertical drive shaft and from the horizontal drive shaft just forward of the u-joints. The extra gaskets were for different applications of the pump kit.
                  Eddie Petty. #3 Dirt Modified
                  Courtland, Virginia
                  V-20 Wellcraft
                  3.7 470 Mercruiser

                  Stumpnocker
                  25 Yamaha, 25 Johnson, 25 Evinrude, 9.9 Evinrude, 4 Johnson, 2.5 Johnson

                  Comment



                  • #10
                    Re: Alpha one Gen 1 raw water pump question.

                    I agree the white tube melted due to no water pumping, it just protects the copper, no big deal if copper looks ok. re the exhaust shutters Im perhaps alone on this but this has been my experience: I got my first MC in 1972 and have owned 4 of them, use every day for commuting and fishing.Prob 8000 hours in total The first few years I would change them if needed, havent bothered for last 30 yrs. Engines last years,never any prob with exhaust valves or such,only issue I ever had was once I was cruising and the wire came off the coil. Dead stop. Engine filled with water from wash coming up the drive... I guess. Oh yeah once the napa dealer sold me a counterrotating starter, that also pumped water into engine. With the exception of these two things, lack of shutters has been a non issue. Replacing them was no fun when I did do it.,You have to remove ex.elbow etc.I wouldnt bother changing them. M.H.O.

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