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mercruiser 4.3 engine won't stop

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  • mercruiser 4.3 engine won't stop

    I have a 2005 Mercruiser 4.3 190 hp in a Bayliner 185. After running for an hour or more the engine will run on after the key is turned off. Sometimes just a few seconds but often for 15 seconds or more? Dealer suggested turning engine off while still in gear but this doesn't seem to help much. Someone else suggested ignition timing may be off but it seems to run well except for getting the engine to stop. The engine has only about 20 hours. Thanks for any advice.

  • #2
    Re: mercruiser 4.3 engine won't stop

    Get it back to the Dealer,+ Get it Fixed,.....

    It'll Cost you a new Motor if you Don't........

    Mercruiser has issued Service Bulletins about it......

    Comment


    • #3
      Re: mercruiser 4.3 engine won't stop

      Yep, timing or idle too high.

      Comment


      • #4
        Re: mercruiser 4.3 engine won't stop

        Originally posted by imported_Coors View Post
        Yep, timing or idle too high.
        Carbon buildup is more likely.

        Comment


        • #5
          Re: mercruiser 4.3 engine won't stop

          Yep, that could do it too.

          Comment


          • #6
            Re: mercruiser 4.3 engine won't stop

            Has it done this since it was new?
            My volvo 4.3 did it from the start. I lowered the idle speed to 600-700 RPM,( idle speed was too fast around 850 rpm)
            and switched to 89 octane fuel. Also I always try to let the engine idle for a few seconds before shutting down. It seems to have stopped the problem.

            Comment


            • #7
              Re: mercruiser 4.3 engine won't stop

              There are bullitins about this.Change gas,plugs,timing,add a carb kit, ....

              First thing I ask my customers to do is tool around the pond a bit before turning the key off,or let her idle for 2 minutes at least.Get the temp down.
              Unfortunately todays gas is made for cars,not boats.

              If your dealer is not aware of this ....... your choice

              DHP

              Comment


              • #8
                Re: mercruiser 4.3 engine won't stop

                Here is a copy and paste of the Mercruiser service bulletin no. 97-17

                = Revised July 1999
                Engine ‘Dieseling’ or ‘Running-On’
                Models
                MCM 4 Cylinder, V6 and V8 with Carburetors.
                Situation

                Under certain conditions, carbureted engines may ‘run-on’ when the ignition key is turned off. Normally, it
                will take a combination of several of the following conditions to make the engine ‘run on’. These conditions
                include but are not limited to:
                1. Type and formulation of gasoline available in the area.
                2. Type of boat and its engine compartment ventilation system.
                3. Outside air, inside engine compartment air and engine coolant temperatures.
                4. How quickly the engine is shut off after running at cruising or higher RPMs.
                5. How the boat and engine are operated.
                6. Engine idle rpm set too high.
                7. Wrong heat range spark plugs or spark plugs with deposits on them.
                8. Deposits in combustion chamber.
                Carbureted engines, unlike EFI, do not shut off the fuel supply to the engine when the ignition key is turned
                off. As the engine is coasting to a stop, air is still flowing through the carburetor into the manifold. This air
                flow can still draw fuel from the carburetor, through the intake manifold and into the combustion chamber.
                A hot spot in the combustion chamber will cause this fuel/air mixture to burn. The engine now ‘diesels’ or
                ‘runs on’ although the ignition system is not firing. EFI engines do not have this problem because the injectors
                do not inject fuel once the ignition key is turned off.
                Suggestion to Minimize ‘Run On’
                Don S.


                Please, no PM's (Private Messages) regarding boat/engine problems.
                That is what the forums are for.
                Only forum/moderator issues will be answered in PM's.

                Comment


                • #9
                  Re: mercruiser 4.3 engine won't stop

                  The boat was purchased new last year. It started doing it last year after being on the water for a few times. Yesterday was first time out this year and it was pretty bad. Idleing before stopping may help, but we're skiers and it's a little impractical when skiers are down. Thanks to everyone for your help.

                  Comment


                  • #10
                    Re: mercruiser 4.3 engine won't stop

                    Aren't you basically at idle picking up the skier?

                    Comment


                    • #11
                      Re: mercruiser 4.3 engine won't stop

                      Engine should be off when skiers are getting on board. We're in the river and trying to get them picked up as quickly as possible when down.

                      Comment


                      • #12
                        Re: mercruiser 4.3 engine won't stop

                        Over the past 2-3 yrs, my '97 4.3 Liter Mercruiser has had the same issue of wanting to still run after ignition turned off.

                        For the 2nd time now, the motor has locked up - wont' turn over. 1st time, I stripped flywheel trying to start it. Local mechanic found water in the cylinder heads but no source of water leak - no cracks in blocks. Compression tests showed 150 on all cylinders but 140 on #3.

                        Just this weekend, it locked again. I took out the spark plugs & blew water out the cylinder heads.

                        The motor ran fine for the first 10 years I had it. The past 2 years, it has had the problem of continuing to want to run after shutting off key. More severe, both times that the motor has locked up.

                        Any suggestions on the source or any good mechanics in the St. Paul/Minneapolis, MN area?

                        Thanks,
                        Mark

                        Comment


                        • #13
                          Re: mercruiser 4.3 engine won't stop

                          Smitty, you need to start a new thread.

                          Comment


                          • #14
                            Re: mercruiser 4.3 engine won't stop

                            Originally posted by rbrandel View Post
                            Engine should be off when skiers are getting on board. We're in the river and trying to get them picked up as quickly as possible when down.
                            This is something I have never understood about skiing... Why does the engine need to be shutdown when picking up a person in the water? If it's to ensure the prop isn't turning, then that's why you have a shift control... It may be a hangover from the old days when ski boats had big old V8s in them that were bolted to a propshaft, without a gearbox. I can well understand it in that situation, but the modern sterndrive does have a gearbox, use it....

                            I work in the offshore industry and we are all well versed (too well versed sometimes) in emergency procedures, that includes recovering people fro the water... The first rule is NEVER shutdown an engine, especially in crowded waters, when picking up people. You need that engine running and ready to go....

                            If you have just been pulling a skier around your engine has been under maximum load and the cylinder temperatures will be sky high.... THAT is the main reason it's running on... Let it idle and get the cylinder temps down....

                            Chris.............
                            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
                            The world takes on a whole new perspective when viewed from 100 below.
                            1972 Bertram Bahia Mar 20
                            2006 Mercruiser 4.3MPI (0W617679) w/Alpha One Gen II (0W829301)
                            (Original - 1972 '165' In-line 6. Previous - 1994 4.3LX)


                            Comment


                            • #15
                              Sign up today
                              Re: mercruiser 4.3 engine won't stop

                              Originally posted by smittys5 View Post
                              Over the past 2-3 yrs, my '97 4.3 Liter Mercruiser has had the same issue of wanting to still run after ignition turned off.

                              For the 2nd time now, the motor has locked up - wont' turn over. 1st time, I stripped flywheel trying to start it. Local mechanic found water in the cylinder heads but no source of water leak - no cracks in blocks. Compression tests showed 150 on all cylinders but 140 on #3.

                              Just this weekend, it locked again. I took out the spark plugs & blew water out the cylinder heads.

                              The motor ran fine for the first 10 years I had it. The past 2 years, it has had the problem of continuing to want to run after shutting off key. More severe, both times that the motor has locked up.

                              Any suggestions on the source or any good mechanics in the St. Paul/Minneapolis, MN area?

                              Thanks,
                              Mark
                              A. Start a new thread
                              B. I bet the manifolds and elbows are original, yes?

                              Chris...........
                              xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
                              The world takes on a whole new perspective when viewed from 100 below.
                              1972 Bertram Bahia Mar 20
                              2006 Mercruiser 4.3MPI (0W617679) w/Alpha One Gen II (0W829301)
                              (Original - 1972 '165' In-line 6. Previous - 1994 4.3LX)


                              Comment

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