Home Forum Ask A Member 1961 Merc 500 Idle Issues

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  • #296707
    Propav8r
    Participant

      US Member

      Hey y’all, I’ve got my ‘61 Merc 500 about ready to go onto my Feathercraft Vagabond, but I’m having issues with it idling.

      I can’t get it to idle down below about 1400 rpm. This obviously makes shifting very rough and I don’t want to put that much wear on the lower unit.

      I feel like this is a timing issue, because my mind says if it was an air leak, I could completely close the throttle plate and it would still idle high. In my case, if I gradually close the throttle plate, the motor will just shut off below about 1350-1400rpm.

      I’ve read the timing procedure in the manual, but I don’t have any of the tools referenced. Is there another way to set timing, maybe with an inductive timing light?

       

      #296761
      Pondrocket
      Keymaster

        Lifetime Member

        Welcome propav8r,

        Need  background on engine first what do you mean by ” about ready to go”? What status is engine currently in. Once that is understood I will get some good feedback and suggestions. Do you have a Master Service Manual & parts list, if so excellent if not i would suggest you get both. For your fishing engine application to time the flywheel and distributor pulley you will need to line up the timing mark on flywheel which is a straight line with the timing mark arrow on the distributor assembly. All is shown section IV-Ignition of manual. Once good there you will need to set max spark advance, adjust carburetor throttle pick up & carb adjustments on yours only low speed high has fixed jets. There is a complete process for all in book. On a side note we do have a members only section on this website with loads of information and videos for all makes and models.

        Travis

         

        Travis
        AOMCI VP Communications
        AOMCI Webmaster
        webmaster@aomci.org

        1 user thanked author for this post.
        #296764
        Michael Anfossi
        Participant

          International Member

          My gut says it is a low speed fuel mixture issue. Have you adjusted the mixture screws on the carbs? Do they make any difference? If not they are probably gummed up.

          #296765
          daytonajohn
          Participant

            US Member

            Install new crankshaft seals then go from there. It might idle just fine after that.

             

            #296791
            labrador-guy
            Participant

              US Member

              I don’t know about your motor but on a 1956 Mark55 the idle is set by adjusting the remote control stop.   Maybe yours is like that?

              dale

              1 user thanked author for this post.
              #296792

              Thanks for this image! Helps a lot!

              #296797
              crosbyman
              Participant

                Canada Member

                https://www.youtube.com/watch?v=MfTpU6HS4cA

                see around 11:00  idle passage

                https://www.youtube.com/watch?v=MfTpU6HS4cA

                 

                no expert on Merc carbs but when I had a problem idling a small 4hp Merc a few years ago  it was suggested I properly clean the idle  passage (small tube) and that instantly  fixed my  idling problem !

                you indicated the engine dies at low rpms below 1200-1400 indicating  a likely fuel supply problem ( timing issues aside if nobody messed with timing and idle stop adjustment etc…)

                your initial post (top) does not say you fully took care of cleaning ALL carb passages  and as per  M.Anfossi’s  suggestion… that may be your  easiest option.

                easy stuff first  !  btw my boating life  years ago  included a Merc 500 and  a Classic 50 (45hp)  4 cyl. and both were superb idlers…all day long.  I have since moved to ETEC technology 75hp 🙂

                 

                btw  please post exact mdl and ser#  !!!

                 

                Joining AOMCI has priviledges 🙂

                #296988
                Propav8r
                Participant

                  US Member

                  I’ll pull the carbs and clean them again. I did already do that once, but who knows, maybe I missed some gunk.

                  Thanks for the input y’all! I’ll start by checking the basics again and go from there.


                  @Crosbyman
                  , my serial number is 1423438. I believe the motor is a Merc 500M that was converted to electric start, but has no charging circuit. I’m not sure though, it could just as easily be a 500E with the charging gear removed.

                  #296989
                  Propav8r
                  Participant

                    US Member

                    Welcome propav8r,

                    Need  background on engine first what do you mean by ” about ready to go”? What status is engine currently in. Once that is understood I will get some good feedback and suggestions. Do you have a Master Service Manual & parts list, if so excellent if not i would suggest you get both. For your fishing engine application to time the flywheel and distributor pulley you will need to line up the timing mark on flywheel which is a straight line with the timing mark arrow on the distributor assembly. All is shown section IV-Ignition of manual. Once good there you will need to set max spark advance, adjust carburetor throttle pick up & carb adjustments on yours only low speed high has fixed jets. There is a complete process for all in book. On a side note we do have a members only section on this website with loads of information and videos for all makes and models.

                    Travis

                     

                    Thanks, just getting back to this post. I’ll check out the members section. I do have both the factory service manual and a parts list. By “ready to go” I mean I’ve done the basic tune up (new plugs, new magneto belt, cleaned points, new rotor, new wires, rebuilt harness, etc)

                    I did not crack the cases open, but it may have been done at some point.

                     

                    #296995
                    crosbyman
                    Participant

                      Canada Member

                      john’s old mercury site is also a place where Merc folks hang out 🙂

                      JohnsOldMercurySite – Index page

                      Joining AOMCI has priviledges 🙂

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