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4.3L Mercruiser loud sucking noise-gctid817842

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    4.3L Mercruiser loud sucking noise-gctid817842

    On my 2007 Bayliner with a 4.3 Mercruiser there is a loud sucking noise coming from throttle body or carb whatever it is. See picture for where arrow points. This is where the loud sucking noise is coming from. Does anyone or has anyone had experience with this same issue? If so what was the remedy? If I put my finger over the hole the engine will pretty much die.



    Attached files


    #2
    That appears to be a mercarb two barrel carburetor. I believe that hole is a venturi bypass for when the lower butterfly valves, those brass colored things at the bottom of the big holes are closed during idle. However, in looking at the age and general condition that I can see in your picture, I suggest taking it to a shop that specializes in performance cars with carburetorated engines like Carb Connection in Redmond, WA. There are differences with marine carbs that make them closer to a racing application than your grandfathers Buick.

    I'm sure someone will chime in with some more definitive information as I'm a four barrel kind of guy. You can help by posting the serial number of the engine, which sounds kinda crazy, but mercruiser changes are connected to serial numbers rather than model year. Kind of a pita until you get used to it.
    P/C Pete
    Edmonds Yacht Club (Commodore 1993)
    1988 3818 "GLAUBEN”
    Hino EH700 175 Onan MDKD Genset
    MMSI 367770440

    Comment


      #3
      If you have the TKS (Turn Key Start) Carb, the noise (AKA hiss), is normal. Does it stop after the engine reaches operating temp.. around 10 minutes or so ?

      Michael
      Huntsville, Alabama
      2009 Bayliner 195 Sport 4.3 TKS
      1979 Basstracker 50hp Mercury "Duck Slayer"

      Comment


        #4
        It used to go away after a little while I believe but now it is making the noise all the time. It's not a hiss. This is like the sound of a vacuum cleaner. I can hear it with the engine cover closed even. Oh and I think it's a turn key start. I put the key in the ignition and turn it to start it.

        Comment


          #5
          Looks to me to be TKS as theres no choke plates!!

          does not look like the Mercarb 2B that was on my 4.3 Merc!

          Just my 2c!

          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


            #6
            If it is in fact the fuel enrichment noise then it should stop after the engine warms up when first cranking. If you have the TKS carb, it will read "TKS" next to the 4.3 on the flame arrestor. Little info about TKS(pulled it from another site).

            The TKS system has been added to carbureted engines to:

            ÔÇó Provide additional fuel to air mixture when starting a cold engine. Idle speed is slightly

            increased by supplying the additional fuel / air mixture required to start a cold engine.

            ÔÇó Prevent enrichment when starting a warm engine.

            COMPONENTS

            1. The TKS carburetor casting allows starting fuel to be drawn from the float bowl and

            mixed with air in a chamber. This enriched mixture is drawn into the engine through an

            opening in the carburetor body below the throttle plate.

            2. The TKS module mounted to the carburetor. When 12V DC is applied, the TKS module

            will warm internally, causing a plunger to extend from the module and close the

            enrichment fuel air passage in the TKS carburetor.

            3. On 3.0L engines, an oil pressure switchprovides a ground (-) path for the TKS module.

            Positive (+) voltage is continuously supplied through a 20 amp fuse directly from the

            engine circuit breaker.

            4. On V-6 and V-8 engines an existing oil pressure switch provides 12V positive (+)

            voltage to the TKS module. Ground for the TKS module is continuously supplied.

            TKS SYSTEM OPERATION

            The TKS Carburetor assembly provides precise fuel and air delivery during startup for all

            temperature conditions. An electrothermal valve, the TKS module, is installed on the

            carburetor assembly.

            Before startup and according to ambient temperature, the TKS Module brass sleeve

            retracts, and the enrichment fuel and air valve is opened.

            The TKS fuel / air passage is normally open, allowing fuel enrichment mixture through the

            carburetor continuously, unless the passage is blocked by the plunger of the TKS module.

            With the key switch in the start position, the vacuum of the engine pulls the enrichment fuel

            and air into the intake manifold.This starts an electrical warming of the module.

            With the circuit completed, the electrothermal TKS module brass plunger extends to block

            the enrichment passage.

            Once the TKS module brass sleeve is fully extended, the enrichment fuel and valve are

            fully closed, and enrichment stops.

            In order to keep the TKS module warming and the starting channel in the carburetor closed

            when engine is warm a second circuit has been added. For additional information, see the

            "Typical Starting System Components" in Section 4A for your particular engine type.

            TKS Starting Characteristics

            On 3.0 L models - If the engine has not run for a long period of time, it might require a

            couple of attempts while the fuel bowl refills. Once the engine has started, it will idle at

            700-900 RPM.

            On 4.3 L, 5.0 L, and 5.7L models - If the engine has not run for a long period of time, it

            might require a couple of attempts while the fuel bowl refills. Once the engine is started, it

            will idle around 650 to 700 RPM in idle stabilization mode. If the idle exceeds 700 RPM,

            the ECM adds spark, thinking that the operator is trying to accelerate, which could cause

            the engine to idle at 700-900 RPM. After the TKS module has shut off the enrichment circuit,

            the carburetor will function like a standard carburetor. If the engine is out of idle stabilization

            mode, (engine below 700 RPM), you will hear and feel a slight drop in RPM. After the TKS

            module has shut off the enrichment passage, the carburetor will function like a standard

            carburetor.

            HISSING NOISE

            There is a small enrichment air passage for the TKS system in the throat of the carburetor.

            Air is drawn through this passage when TKS is in starting mode and does create a slight

            whistle or hissing noise. After 6 to 10 minutes when engine has warmed and TKS system

            has closed the noise will quit and will only occur again after a cold engine start. If this noise

            continues after 10 minutes, this could indicate a problem with the TKS module. See Section

            5B.
            Huntsville, Alabama
            2009 Bayliner 195 Sport 4.3 TKS
            1979 Basstracker 50hp Mercury "Duck Slayer"

            Comment


              #7
              So from reading that it sounds like there is an issue with the TKS module.

              Comment


                #8
                Yes the solenoid sticks.

                When you see it might not be too bad and you can clean it up.

                Give this a quick read:

                http://boatinfo.no/lib/mercruiser/ma...ser41.html#/48

                See how i'm behaving didn't write sucks ... Oooops !
                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


                  #9
                  Ok so yes my boat is equipped with a tks module. Took it off tonight and it looked clean to me. The brass plug looked fine. So what I did find after doing some more digging around is that when trying to find voltage for the tks module I didn't find any. I don't know if you have to actually start the boat or just turn the key to the position where the alarm is going off. I just turned it to that spot and checked for voltage and didn't get any. This was measured at the plug that would plug into the tks module. So I was doing some more digging around and on the wiring harness I was following it back not far from where the two wires split off that go to the tks module and came across another set of wires that just had a cap over one of those wiring plug looking things. I took it off and noticed a small 20 amp fuse is housed inside of this. Plus this fuse is blown. Confusing thing to me is that the boat seems to operate fine so how could a 20 amp fuse be blown and everything pretty much work? Does anyone know what this 20 amp fuse is for? Could it be the culprit for not having any voltage at the plug for the tks hence why the tks isn't working properly?

                  Comment


                    #10
                    I think you found your problem! Simple fix.

                    The 20 amp fuse is between the circuit breaker and the TKS module for protection. When power is applied (Start Key turned on), the electro-thermal TKS module brass plunger extends to block

                    the enrichment passage. If no power is applied to the TKS Module, the enrichment fuel and air valve stay open continuing enrichment (air being pulled through the small enrichment valve)....AKA, the hissing noise.

                    I would now be concerned how the fuse blew.

                    Michael
                    Huntsville, Alabama
                    2009 Bayliner 195 Sport 4.3 TKS
                    1979 Basstracker 50hp Mercury "Duck Slayer"

                    Comment


                      #11
                      I can't find this fuse in the bayliner manual wiring diagram though. So a few weeks ago we were out in the water and I believe in my welcome to boc I wrote about how the 15 amp accessories fuse blew and then the boat wouldn't start. Anyway it was weird cause it started fine although my boat seems to start fine when cold but it's a little harder to want to start after it's been running a bit. It doesn't seem to much like the turn on then off then on etc. Anyway I was pulling my son around on the wakeboard and he went down so I got to him and turned the boat off then went to start it and it didn't crank over right away so I turned the key off then back to try and start and nothing. So it could have been from short stroking it when trying to start it if you know what I mean and that could have blown them. I'll replace the 20 amp and see how it goes. I haven't had any probs with the other since replacing it and not short stroking the ignition when trying to crank it over. Thanks for the help thus far and I'll let you know the outcome.

                      Comment


                        #12
                        No problem! I'm no mechanic, but have had my fair share of problems to work through. It can get very expensive if its taken to the shop every time somethings not right. Sometimes we have to lean on other Boat owners for help to keep the sport affordable!
                        Huntsville, Alabama
                        2009 Bayliner 195 Sport 4.3 TKS
                        1979 Basstracker 50hp Mercury "Duck Slayer"

                        Comment


                          #13
                          Well I replaced the fuse and had it running at home. Hooked up with fresh water etc so I wouldn't blow up the engine. Anyway after the boat got to normal operating temp the solenoid closed and the loud hissing went away.

                          Out on the lake today though everything was well. However the fuse blew again. If this is just a fuse that protects the TKS then could something be wrong with the module itself causing the fuse to blow like a short in it or overheating or what?

                          Any help would be greatly appreciated.

                          Comment


                            #14
                            I would unhook the wire from the module run a fresh wire fused from the battery straight to the carb, see if that fixs it, then latter wrap it to the wire harness.
                            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


                              #15
                              So today I put in a new diode. New 15a and 20a fuses. Everything was great. Tks module heated up and closed. Engine was purring along just fine. The it just shut off. Found that both the 20a and 15a fuse were blown. Replaced the 15a fuse. Left 20a blown. Engine would try to turn then stop. Checked 15a fuse and it was blown again. Unhooked tks module and same thing. Unhooked diode and no fuses blew. Put old diode assy back in and it ran same as before. I can have the old diode in. Both fuses ok but tks module doesn't close. I am confused as to what is going on. Plus I have two pics if someone can tell me what they are.

                              I'm not sure if I know how in the previous post how to wire the tks module straight from the battery with a fuse. I'd rather find the problem and fix it. I was looking at the wiring diagram for the Tks that was on another forum and can't find the temp switch on the engine. Please help. Thanks.

                              Comment

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