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1988 70hp intake manifold?

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  • 1988 70hp intake manifold?

    Is the valve reed gasket a must have to replace the intake gaskets?

    I purchased the other 2 and the valve reed gasket was obsolete. Should I make one from gasket maker?

    Also on my 2 lower carbs the pilot jet ports are plugged. Should my top carb have a plug too?

  • #2
    All of the gaskets are available. All three have had part number changes.

    By saying "pilot jet ports are plugged" are you referring to access to the idle mixture screw being blocked by a small disc?

    If so, those are referred to as EPA tamper proof plugs. They are intended to keep folks from making the motor run better/like it should by blocking access to the idle mixture screw. Early motors did not have them. Later motors did. Maybe someone replaced the bottom two carburetors with later model year versions.

    6H3-13621-00-00 } 6H3-13621-A1-00

    6H3-13622-00-00 } 6H3-13622-A1-00

    6H3-13624-00-94 } 6H3-13624-00-00


    • #3
      Thanks for the part numbers!

      The plug I'm talking about is plugging the small jet inside the carborator. I cleaned my carbs with sea foam today but carb 2 wasn't getting gas so I took them off to clean and discovered the plugs in the bottom and middle carbs not the top. Best I can find is that it's an air restrictor needed to maintain fuel/air mixture ratios but it was only in the bottom 2 carbs. I'm thinking the top is supposed to have one too. Or none needed?

      I'm interested in hearing more about the plugs u are referring to. Sounds like performance. 👍🏻


      • #4
        Or we are talking about the same thing because I believe the small jet is the idle screw?
        Last edited by Asimpson74; 06-02-2017, 11:08 PM.


        • #5
          I think you are talking about part # 676-14966-00-00. Typically, yes that plug

          should be there. Take a look inside the bore where that plug sits. I think that

          you will see a small fuel or fuel mixture passage that gets blocked off when

          that plug is installed correctly.


          • #6
            Originally posted by Asimpson74 View Post
            Or we are talking about the same thing because I believe the small jet is the idle screw?
            It will help us to help you if you will provide the complete model identity of your motor and then use the parts catalog to specify which particular component you are referring to. Here is the link to an exploded view of a 1998 70 HP carburetor. Are you talking about item 6? Referred to as a "cap" by Yamaha.

            Note that the parts book shows three as being used. Three carburetors. One for each carburetor. They need to be installed.

            1988 70ETLG Yamaha Outboard CARBURETOR Diagram and Parts


            • #7
              The parts diagram for your carb(s):

              1988 70ETG Yamaha Outboard CARBURETOR Diagram and Parts

              Jets 4, 5 and 6 should be removed fully and cleaned. These are the ones that clog and cause issues..

              The air screw, part #25, can be pulled and cleaned(check # of turns BEFORE removing fully)

              I'd use a brake or carb cleaner on those jets, much more effective than SF..

              Last edited by TownsendsFJR1300; 06-03-2017, 07:37 AM.
              1997 Angler 204 CC, 2006 F150 TXR


              • #8
                the rubber cap/plug would be #7 not #6.

                my C40 has them also.
                there is a passage between those jet passages.
                it forces the fuel that runs thru that jet to flow thru the main jet 1st.
                My thoughts are that if left open(cap missing) the motor could draw more fuel than it needed/ or designed to have.
                with it in place the main jet regulates how much fuel is used by both jets


                • #9
                  Thanks for all your help! The plug is part #7 and I will install it in top carb like the other 2. Might explain my tuning issue with the motor. Will probably replace all 3 with new ones to be safe. I have already cleaned the carbs so thanks for the info!


                  • #10
                    Back to the intake gaskets....when I install the new gaskets should I use gasket sealer...ultra orange or ultra black or none?


                    • #11
                      You don't need any sealer.

                      Look at the old gaskets/block, there is none...

                      Torque to spec or just "good and snug"..
                      1997 Angler 204 CC, 2006 F150 TXR


                      • #12
                        Great! thanks