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    replaced impeller but still overheating

    2007 Bayliner 175
    MerCruiser (MCM 3.0L TKS)
    Alpha 1
    Serial:# 1A011021

    Hi folks -

    Took my boat out of storage this weekend (everything working great when put away last fall). Hooked block and exhaust drain lines back up, put garden hose and muffs on and started engine. As engine started warming up I was surprised that water wasn't pissing out the back as it usually does. At just over 175 I shut the boat off and allowed it to cool down. I checked for water in the block (i.e. disconnected drain lines) and there was no water at all!

    Buddies suggested impeller was the problem so I dropped the lower leg, replaced the impeller, put everything back together and tried on muffs again. Same thing. Overheated (or would have if I had let it continue) and again there was no water in the block when I checked after it cooled back down.

    So evidently impeller is not the problem. What should I check next?

    thx for any helpful advice
    Dean

    #2
    Is water coming out the transom ports on either side of the drive? If so the thermostat may be stuck closed with air in the block
    1997 Maxum 2400 SCR 5.7LX Bravo II

    Mike

    Comment


      #3
      hi Nauti_Mike - - no water at all out of the exhaust ports ... there's a little bit sputtering out around the prop

      Comment


        #4
        See the long hose that connects to the t-stat housing that travels over the engine from the transom.

        Remove the hose off the t-stat housing place in bucket put water to the drive start engine for 15 seconds shut off and post back how much water is in the bucket, we will go from there.
        Be good, be happy, for tomorrow is promised to no man !

        1994 2452, 5.0l, Alpha gen. 2 drive. Sold ! Sold ! Sold !

        '86 / 19' Citation cuddy, Merc. 3.0L / 140 hp 86' , stringer drive. Sold ! Sold ! Sold !

        Manalapan N.J

        Comment


          #5
          Originally posted by Chief_Alen View Post
          See the long hose that connects to the t-stat housing that travels over the engine from the transom.

          Remove the hose off the t-stat housing place in bucket put water to the drive start engine for 15 seconds shut off and post back how much water is in the bucket, we will go from there.
          Agree. Remove the hose coming from the transom assembly to verify flow from the raw water pump. If no flow there is either a blockage in the intake of the drive, leak at the raw water pump preventing pressure or blockage after the pump. May also be poor seal from pumps output to upper water tube in the upper half of the drive.
          1997 Maxum 2400 SCR 5.7LX Bravo II

          Mike

          Comment


            #6
            Exhaust elbows plugged.
            Don
            1995 Maxum 2400 SCR LUNA DE MIEL
            1988 Bayliner 2455 (sold)
            1976 Tahiti 16.5 I/O (sold)
            10 ft livingston (lost in fire )
            1987 18ft. Seaswirl cuddy (lost in fire)
            "Is it better to be on a boat thinking about God, or be in church thinking about boating?"

            Comment


            • Nauti_Mike
              Nauti_Mike commented
              Editing a comment
              But why is the block dry, no water? I think the first thing to check is water even getting to the thermostat housing.

            #7
            We have to first find out if he has good water coming to the engine.
            Be good, be happy, for tomorrow is promised to no man !

            1994 2452, 5.0l, Alpha gen. 2 drive. Sold ! Sold ! Sold !

            '86 / 19' Citation cuddy, Merc. 3.0L / 140 hp 86' , stringer drive. Sold ! Sold ! Sold !

            Manalapan N.J

            Comment


              #8
              Even if the actual thermostat was stuck closed, the T-stat housing would still allow the bi-passing seawater to enter and exit with the exhaust system. In which case, you should have seen water coming out of the transom unit and/or out from the center of the propeller.

              I would sooner think that you have an issue right at the seawater pump itself.



              I checked for water in the block (i.e. disconnected drain lines) and there was no water at all!
              If this is equipped with what some refer to as the single point drains, I would get rid of those ASAP.
              Rick E. Gresham, Oregon
              2850 Bounty Sedan Flybridge model
              Twin 280 HP 5.7's w/ Closed Cooling
              Volvo Penta DuoProp Drives
              Kohler 4 CZ Gen Set

              Comment


                #9
                As others have suggested: verify there is water flow from the drive using the 15 second test. Btw: when using “muffs” the pressure from the city hose can give you a better flow rate, the drive should be submerged and pulling its own water for an accurate test.
                heres what the flow rates are:
                Click image for larger version

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                Attached Files
                Dave
                Edmonds, WA
                "THE FIX"
                '93 2556
                Carbureted 383 Vortec-Bravo II 2.0:1 18 1/4x19 P

                The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
                Misc. projects thread
                https://www.baylinerownersclub.org/f...56-gctid789773

                Comment


                  #10
                  hi guys - Original poster here ... sorry but I haven't been able to get to do the volume test suggested above - unfortunately I only have my back yard to work in and its been pouring rain for past couple days. I may have to rig a tarp or something if this rain keeps up as is forecast ... :-(

                  Comment


                    #11
                    Post back when you have a chance, we understand.

                    You could place the drive in a tub, garbage can, even on the muffs i don't think you got good water coming thru to the engine.
                    Be good, be happy, for tomorrow is promised to no man !

                    1994 2452, 5.0l, Alpha gen. 2 drive. Sold ! Sold ! Sold !

                    '86 / 19' Citation cuddy, Merc. 3.0L / 140 hp 86' , stringer drive. Sold ! Sold ! Sold !

                    Manalapan N.J

                    Comment


                      #12
                      hi Chief… you are correct... I pulled off the intake hose and started the engine. After slightly more than 20 seconds running there was NO water at all coming thru the intake hose. I'm going to put the boat into the lake and see if it pulls water that way … my son has an outboard that doesn't pull water on muffs but works fine when 'submerged'. I'll report back again in couple hours.

                      Comment


                        #13
                        Originally posted by DeanPeddle View Post
                        hi Chief… you are correct... I pulled off the intake hose and started the engine. After slightly more than 20 seconds running there was NO water at all coming thru the intake hose. I'm going to put the boat into the lake and see if it pulls water that way … my son has an outboard that doesn't pull water on muffs but works fine when 'submerged'. I'll report back again in couple hours.
                        I’ll be surprised if the results are any different. When you replaced the impeller did you use the guide tube to ensure the upper water tube engaged into the water pump housing? Verify the intake of the drive is clear, holes on either side where you attached the muffs.
                        1997 Maxum 2400 SCR 5.7LX Bravo II

                        Mike

                        Comment


                        • DeanPeddle
                          DeanPeddle commented
                          Editing a comment
                          hi Nauti-Mike: yeah I was careful to make sure the water tube engaged properly. regarding the intake holes of the drive - I didn't see any blockages but I'll look again.
                          Question: In the lower unit, I removed the impeller housing and replaced the impeller, the gaskets and the strike plate underneath that. Below the plate there was a yellow 'cone'. No idea what it does. Should I have removed that as well? Is there access to the interior of the lower unit beneath that cone? i.e. Is there a way to check for a blockage below the impeller ?

                        #14
                        hi - so I just put the boat in the lake and ... everything's good! I didn't go for a run yet - just idling at the dock - but there's lots of water coming out the intake pipe at the thermostat. I reattached the hose and after about 5 minutes the Temperature rose to 175 (typical) and held there. So basically I'm getting no water with just the muffs but lots of water when submerged. I'm going for a short run in a few minutes and will let you know how that goes.

                        Comment


                        • DeanPeddle
                          DeanPeddle commented
                          Editing a comment
                          just went for a long(ish) run on the lake and everything's tickity-boo! :-)
                          temperature stayed around 175 the whole time. I'm thrilled that I'm no longer land-bound but would like to get the muffs working as well.

                        • Nauti_Mike
                          Nauti_Mike commented
                          Editing a comment
                          Rather interesting results, try the muffs again and let us know how it goes.

                        #15
                        Maybe bad muffs ( no DIVING jokes ).
                        Be good, be happy, for tomorrow is promised to no man !

                        1994 2452, 5.0l, Alpha gen. 2 drive. Sold ! Sold ! Sold !

                        '86 / 19' Citation cuddy, Merc. 3.0L / 140 hp 86' , stringer drive. Sold ! Sold ! Sold !

                        Manalapan N.J

                        Comment

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