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1992 5.7 merc running too rich for too long at start up-gctid398234

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    1992 5.7 merc running too rich for too long at start up-gctid398234

    Hello all, my 5.7 Mercruiser seems to be running too rich for too long at start up. It takes about 15min before the black smoke clears. If I engage the gear before it clears she stalls and it takes a while to start it up again, I presume its flooded with fuel. The temp comes up as normal. When started and fully warmed up it starts up fine for the rest of the day even being left fot three hours or so.

    Any ideas guys?

    Thanks

    Mike

    #2
    Check to make sure the flame arrestor is clean. Beyond that it sounds like a carb rebuild is at hand.
    1989 Avanti 3450 Sunbridge
    twin 454's
    MV Mar-Y-Sol
    1979 Bayliner Conquest 3150 hardtop ocean express.
    Twin chevy 350's inboard
    Ben- Jamin
    spokane Washington

    Comment


      #3
      If this is a conventional carburetor with a choke chimney and choke plate, try re-adjusting the helix tension on the choke plate while the engine is stone cold.

      Make sure that the heating element is working well, and make sure that as it warms the helix, the helix linkage is pulling the plate open.

      .
      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


        #4
        Thanks Dave, the arrestor looks fine but will double check, hope its not a rebuild.

        Gotta have a good look again Rick as Im not familliar with the workings of the carb. I presume the heating element is immersed in the water jacket of the engine (which works like the thermostat in the cooling system) then linked mechanically to the helix. Would I be reasonably correct in this assumption or am i way off once again

        Comment


          #5
          Mike, I don't know when Merc went to their own carburetor for this engine.

          Like said, if this is a conventional carburetor, the choke plate will be pulled OFF via a helix that is electrically heated.

          An engine model number, or perhaps a photo or two would help.
          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


            #6
            Rick may be right about the choke. I was tired when I posted and wasnt thinking the whole thing through.
            1989 Avanti 3450 Sunbridge
            twin 454's
            MV Mar-Y-Sol
            1979 Bayliner Conquest 3150 hardtop ocean express.
            Twin chevy 350's inboard
            Ben- Jamin
            spokane Washington

            Comment


              #7
              Thanks guys, I know the info is sketchy, must row out and bring it in to dock off a swing mooring, put her out five weeks ago and havent seen a fine day yet so Im not missing any boating. Hope to get a good day this week , take a few pics and post them up, i know the engine and outdrive numbers are on a sticker on the carb cover.

              I do suspect its a choke issue also as this rich running only occurs from a first start of the day then starts and runs fine for the remainder.

              Thanks again

              Rgds

              Mike

              from rain soaked Ireland, no wonder the place is so green:livid:

              Comment


                #8
                Heres a few pics of my carb, cant seem to see any electrical connections to the choke but appers that when the helix expands the link rod seems to be rubbing off the plastic cover, hadnt time to look at it closer as I had my two little daughters with me on the day.

                Attached files [img]/media/kunena/attachments/vb/706012=29948-IMAG0512.jpg[/img] [img]/media/kunena/attachments/vb/706012=29949-IMAG0513.jpg[/img] [img]/media/kunena/attachments/vb/706012=29950-IMAG0514.jpg[/img] [img]/media/kunena/attachments/vb/706012=29947-IMAG0515.jpg[/img]

                Comment


                  #9
                  That appears to be a Rochester Quadrajet carburetor with what some refer to as a "divorced" choke.



                  The Helix is actually picking up heat directly and mechanically from the exhaust cross-over within the intake manifold.

                  I'm going to suggest that the Helix is shot from 'ole Father Time, and needs to be replaced and re-adjusted.

                  Your engine serial number should get you to Merc's parts break down.

                  Or..... you contact a good Rochester source, and see if there is a conversion kit to bring this to a Helix affair that uses the electric heating element, and then abandon the OEM system........ but I don't know if such a thing exists.

                  .
                  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


                    #10
                    Take it to a carb repair facility and not to "Joe's Place" under the big oak tree. A real rebuld shop can clean and replace pieces parts that are not included in the typical off the shelf kit. Once done, all you will have to do is adjust the idle.

                    Vic

                    Ft Myers
                    Vic Stewart SN
                    Past Commander
                    Cape Fear Power Squadron
                    Ft Myers Power Squadron
                    1998 2859 7.4 L/B2
                    Raw water cooled

                    Comment


                      #11
                      Vic Stewart wrote:
                      Take it to a carb repair facility and not to "Joe's Place" under the big oak tree. A real rebuld shop can clean and replace pieces parts that are not included in the typical off the shelf kit. Once done, all you will have to do is adjust the idle.

                      Vic

                      Ft Myers
                      +1. Sometimes the shops have a rebuild sitting on the shelf and will swap you.

                      Comment

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