Engine throttle is lacklustre under load

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  • idreamOfSailing
    Senior Member
    • Jun 2018
    • 37

    Engine throttle is lacklustre under load

    I just replaced my carburetor with a new one from Moyer. It seems to be running okay as it starts, idles and throttles up well when disengaged from gear, however when in forward gear the engine seems rather dull and does not accelerate when giving it throttle the way it used to. It doesn't seem to rev up anymore. Also, maybe it's my imagination but it seems to be making a dull, slight thumping sound. I'll check the plugs for spark and try a compression test too but just wondered in the meantime if anyone has any ideas as to what it can be.
  • ndutton
    Afourian MVP
    • May 2009
    • 9601

    #2
    Something to check

    Check the advance weights inside the distributor under the points plate. Please do this without removing the distributor from the engine to preserve the timing.

    Does applying choke make any difference?
    Neil
    1977 Catalina 30
    San Pedro, California
    prior boats 1987 Westsail 32, 1970 Catalina 22
    Had my hands in a few others

    Comment

    • idreamOfSailing
      Senior Member
      • Jun 2018
      • 37

      #3
      Thanks ndutton, but I have no idea of what you just said. I have to do what?

      Comment

      • ndutton
        Afourian MVP
        • May 2009
        • 9601

        #4
        Originally posted by idreamOfSailing View Post
        Thanks ndutton, but I have no idea of what you just said. I have to do what?
        Page 3-3 in your Moyer Marine Service and Overhaul Manual including pictures. Please confirm you have the manual.
        Neil
        1977 Catalina 30
        San Pedro, California
        prior boats 1987 Westsail 32, 1970 Catalina 22
        Had my hands in a few others

        Comment

        • idreamOfSailing
          Senior Member
          • Jun 2018
          • 37

          #5
          Hi, I do not have the manual, didn't know there was one. I have electronic ignition, would the manual still help?

          Comment

          • Surcouf
            Afourian MVP, Professor Emeritus
            • May 2018
            • 361

            #6
            Originally posted by idreamOfSailing View Post
            Hi, I do not have the manual, didn't know there was one. I have electronic ignition, would the manual still help?
            honestly, unless you want to sell the boat in a few weeks... you cannot make a better investment. Will save you a fortune in ignorant mechanics, make your engine reliable and trustworthy.



            And make sure to check the videos... there is one on ignition!!!
            Surcouf
            A nostalgic PO - Previously "Almost There" - Catalina 27 (1979)

            Comment

            • idreamOfSailing
              Senior Member
              • Jun 2018
              • 37

              #7
              Now that's a good idea...there's been something or another wrong with this thing for the last six years I've had it...selling it seems really good right now but I'm not one to pass on my problems to unsuspecting others.

              I've got the manual in my cart now. And you're right about ignorant mechanics, I guess the old axiom is true, if you want a job done right you have to do it yourself!

              It's not an ignition thing though, she starts fine and idles fine, just doesn't seem to have any life under load.

              Thanks for the help.

              Comment

              • ndutton
                Afourian MVP
                • May 2009
                • 9601

                #8
                Originally posted by idreamOfSailing View Post
                Hi, I do not have the manual, didn't know there was one.
                That is NOT what I was hoping to hear.

                I have electronic ignition, would the manual still help?
                Oh yeah, in spades.
                Neil
                1977 Catalina 30
                San Pedro, California
                prior boats 1987 Westsail 32, 1970 Catalina 22
                Had my hands in a few others

                Comment

                • Surcouf
                  Afourian MVP, Professor Emeritus
                  • May 2018
                  • 361

                  #9
                  [QUOTE=idreamOfSailing;126316]

                  It's not an ignition thing though, she starts fine and idles fine, just doesn't seem to have any life under load.
                  /QUOTE]

                  the weights and springs of the distributor are not for starting / idle, but for only load operation
                  Surcouf
                  A nostalgic PO - Previously "Almost There" - Catalina 27 (1979)

                  Comment

                  • JOHN COOKSON
                    Afourian MVP, Professor Emeritus
                    • Nov 2008
                    • 3500

                    #10
                    Originally posted by idreamOfSailing View Post
                    . It doesn't seem to rev up anymore. Also, maybe it's my imagination but it seems to be making a dull, slight thumping sound.


                    Is something fouling the prop that is hitting the boat?

                    ex TRUE GRIT
                    Last edited by JOHN COOKSON; 07-23-2021, 03:01 AM.

                    Comment

                    • joe_db
                      Afourian MVP
                      • May 2009
                      • 4474

                      #11
                      Originally posted by idreamOfSailing View Post
                      I just replaced my carburetor with a new one from Moyer. It seems to be running okay as it starts, idles and throttles up well when disengaged from gear, however when in forward gear the engine seems rather dull and does not accelerate when giving it throttle the way it used to. It doesn't seem to rev up anymore. Also, maybe it's my imagination but it seems to be making a dull, slight thumping sound. I'll check the plugs for spark and try a compression test too but just wondered in the meantime if anyone has any ideas as to what it can be.
                      A swim is in order!
                      Joe Della Barba
                      Coquina
                      C&C 35 MK I
                      Maryland USA

                      Comment

                      • idreamOfSailing
                        Senior Member
                        • Jun 2018
                        • 37

                        #12
                        I'm ordering the manual but it's going to take time to get here (Ontario). In the meantime does anyone have Page 3-3 of the Moyer Marine Service and Overhaul Manual to share here so I can start work now?

                        Comment

                        • jcwright
                          Afourian MVP
                          • Jul 2012
                          • 158

                          #13
                          This is one of the MMI videos that surcouf mentioned in a previous post:



                          It shows how to inspect the advance mechanism.

                          The Moyer overhaul manual is under copyright, which is why you’ll see people on the forum refer to it but not post copies.

                          Hope the video helps you get started. Feel free to ask if you get stuck.

                          Jack

                          Comment

                          • joe_db
                            Afourian MVP
                            • May 2009
                            • 4474

                            #14
                            You still need to look under the boat before you get into anything else.
                            Joe Della Barba
                            Coquina
                            C&C 35 MK I
                            Maryland USA

                            Comment

                            • idreamOfSailing
                              Senior Member
                              • Jun 2018
                              • 37

                              #15
                              I'll slip into the water tomorrow to have a look.

                              Comment

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