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185 3.0 over runs with key off...any ideas??-gctid380882

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    185 3.0 over runs with key off...any ideas??-gctid380882

    I have a 2010 185 Ive had a few problems with it already resulting in new a new carb for the dealer. It ran good at the end of last year after everything was said and done, i winterized it and took it out a few times this year with one problem now.... when i shut the key off the motor still over runs like a old Volvo for a good 10 to 15 seconds.. if i trim the out drive up its not as bad but will still do it SOMETIMES.. but with the out drive trimmed all the way down it does it every time... anybody ever herd of this?? the dealer said it was bad gas but i ran 2 tanks of gas through if with dry gas and i get it from the pump. (ive run my car truck and jet skis with no problem) so i dont think its that.. dealer is over an hour away so i was hoping someone on here as a bit of a idea.. any info is appreciated thanks....Mike

    #2
    How you running it ?

    This is how i run a carbed motor. Cold i pump the throttle 2-3 times leave the throttle down 1/3 of the way and crank it. It starts i leave the throttle alone should run at about 1000-1500 rpm. Choke opens you hear the engine change, put the throttle in neutral for another minute or 2.

    Then i slowly give throttle till i'm at say 3000-3500 rpm i run 2/3 wot.

    I want to stop i slowly back off the throttle till i come to a stop put throttle in neutral and allow the engine to run at least 4-5 minutes at idle.

    Shut off motor. Say i want to start after 30 minutes i try it in neutral no pumping nothing, crank it should start.

    No start then a pump or 2 and back into neutral and crank no start then it's 1/3 down the thottle as a cold start.

    Why i just write all this cause the idle at warm up and idle before shut down
    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

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      #3
      Make sure the idle rpm is what it is supposed to be. If it is fast it will cause run on...

      There may be other causes, someone will chime in.
      1979 32 Uniflite Sport Sedan twin 270 crusaders
      2003 Bayliner 2152 210 Classic 5.0 mercruiser - sold
      I wish I knew now what I didn't know then

      Comment


        #4
        thanks for the input guys.. what should neutral idle be at?? as for the start up and warm up, its the newer model no need to pump the throttle, turn the key and she fires right up. They told me that was something that was changed for the 2010 model. i live 5 minutes from the water so what i do is start boat on the trailer, let it idle for a minute or so while i put stuff in the boat, then back boat off trailer and idle speed to the dock, dock it and then pull the truck out of the water while boat is warming up. so boat is running for a total of 5-6 minutes before its driven. to shut off i just come to a stop put in neutral and shut it off. whats weird is adjusting the trim effects the way it turns off..

        Comment


          #5
          It seems that the 3.0L is prone to this more so than other engines.

          The factory tends to lean out the low speed circuits.

          Cutting ignition does not cut fuel/air supply...... only spark ignition, so this fuel/air is stil being drawn into the cylinders.

          Some suggest that timing is the culprit, but remember, when we turn the key off, the spark ignition is cut.

          However, timing can be the culprit if too much timing advance is causing the engine to run hot while working it.

          Hot pistons and/or valves (that are holding onto any carbon deposits), will create an ignition source, and can ignite the lean fuel/air mixture and you get this run-on.

          Try fattening up the low speed circuits.

          Make sure that the idle RPM is set at factory specs.

          Give it a few minutes to cool down before you turn the key off.

          And yes, higher octane fuel does help.
          Rick E. Gresham, Oregon
          2850 Bounty Sedan Flybridge model
          Twin 280 HP 5.7's w/ Closed Cooling
          Volvo Penta DuoProp Drives
          Kohler 4 CZ Gen Set

          Comment


            #6
            I use 89 from the gas station (keep boat on trailer) does anyone know the proper idle rpm?? or where it should be set to?? also which is the low speed screw and do i have to tighten or loosen it to richen the mixture?? thanks..

            Comment


              #7
              use 93 octane and your problem will be gone. I am on my 3rd boat with the 3.0 and only 93 octane will not run on after hot run with no run on. You can't let the engine idle for 5 mins when you pulling tubes or water skiing and so on.

              you need to be able to shut the boat right off when they need to get back in the boat.

              Try a few tanks of 93 and you will not run any thing else again.

              Comment


                #8
                nh boater wrote:
                use 93 octane and your problem will be gone. I am on my 3rd boat with the 3.0 and only 93 octane will not run on after hot run with no run on. You can't let the engine idle for 5 mins when you pulling tubes or water skiing and so on.

                you need to be able to shut the boat right off when they need to get back in the boat.

                Try a few tanks of 93 and you will not run any thing else again.
                Yep, I use 95 octane on my V6 which are supposed to be renown for running on.

                Never had a problem since.

                NH boater is correct about towing skiers and tubers.

                Comment


                  #9
                  In the water,warm motor, in gear 650-750 " I " consider proper idle speed. The lower the better. Mine idles perfectly at 600. Run on can be caused by carbon on top of the pistons.

                  The motor can actually be running backwards and draw water into the cylinders.

                  Try shutting down if you have to in gear.... pull back the throttle slowly and when at idle in gear shut off the motor.

                  And yes i do agree timing,and carb setting can cause the problem.
                  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


                    #10
                    ok so my idle is definitely a little high then. im around 1000 in neutral with warm engine. ill try lowering that the next nice day we have and ill fill her with 93 next time since shes full of 89 right now.. how about richening it up at idle?? where is the low speed screw?

                    Comment


                      #11
                      Like said earlier.... timing can be part of the issue if it leads to higher cylinder temperatures while running hard.

                      Example: Too much spark lead per RPM and load.

                      Excessive BASE advance may also cause higher idle RPM, until adjusted down.

                      Otherwise, spark ignition is killed when the ignition key is turned off.

                      Yes... carbon deposits are what hold onto the heat that will continue to ignite the rather lean fuel/air mixture.

                      As for the low speed metering. You'll need to see if this carburetor allows for an external adjustment. Some do/some do not.

                      These will be air screws, and will control the amount of air that the low speed circuits can pull in and mix with the available low speed circuit metered fuel.

                      Less air = enriched mixture.

                      More air = leaned mixture.

                      .
                      Rick E. Gresham, Oregon
                      2850 Bounty Sedan Flybridge model
                      Twin 280 HP 5.7's w/ Closed Cooling
                      Volvo Penta DuoProp Drives
                      Kohler 4 CZ Gen Set

                      Comment

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