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aq125a stalls at 1400 rpm when under load

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  • aq125a stalls at 1400 rpm when under load

    I have a 83 Bayliner Capri with an AQ125a and 270 out drive. This is my first boat and I bought it last year. It has always had an issue where it seems to have a dead spot between 1400-2000 RPM where if I accelerate slowly it will bog down and die. If I punch it the engine revs right up and I can be cruising at 40 MPH without an issue.

    I did a carb rebuild with a kit from Mikes Carbs. last year but it didn't seem to help. I have tried adjusting the accelerator pump too but that hasn't helped either. I figured I either didn't do a good enough job cleaning the carb (it was pretty clean when I rebuilt it) or something else is wrong (maybe accelerator pump spring is going, etc) and I was planning on trying to get a replacement carb this winter or taking the current cab and doing a full dip in carb cleaner.

    However, I'm now wondering if it is something else. I was on the lake this weekend and I had the boat to myself and I discovered I can move through the RPM range with no difficulties if the drive is in neutral. It only bogs down when it is in drive. Could there be something else causing the engine to bog down? Could a damaged prop do this? I serviced the outdrive last fall so it has fresh oil. The old oil was clean and looked new.


  • #2
    You still have a carb issue, reving the motor up in neutral tells you nothing. The motor takes a very-very small amount of gas to rev up to wide open. In the water and under load it takes a lot of fuel to get it up on plane. A damage prop will cause vibration but will not cause a bogg

    See if your getting a full and complete stream of fuel from idle to almost WOT from the accelerator pump. If there are breaks in the stream then this needs fixed
    94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
    95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
    07 Seadoo GTX
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    G-Dad always said "First Liar doesn't stand a chance"


    • #3
      I don't know this drive/engine/etc but an ignition coil can be a thing that is often overlooked. It usually isn't a source of problems, but they do seem to have a 20-25 year lifespan.....which is excellent in general.

      The electrical "load" or resistance on an ignition spark increases the higher the cylinder pressure, which is a fancy way of saying that the more the throttle is opened the more the spark is challenged to deliver the energy needed to jump the gap in the combustion chamber under considerable "density" of the charge mix. Where there are issues like the coil winding is corroding and breaking down or a spark plug wire is rubbed thru somewhere due to chafing, the proper ignition energy isn't being delivered.

      So this is just one thing to check along your troubleshooting path. The model year of 1983 jumped out at me as I know that was a few years ago


      • #4
        If the coils working at low speed then high??
        I wouldn't think there's a problem.
        Test: start and get running, let motor come up to temp.
        Then touch the coil, if it's too hot to keep your finger on it?? Then it's possibly bad.

        But like AllDodge said the carbs probably the problem.
        Have it professionally done.

        Buy American made Cars and Trucks!!!Towing insurance for a boat,a GREAT thing.
        ​Tools to make my life easier: Battery tester, die grinder, temp.gun, compression tester, DVA meter.

        In Scenic , Beautiful San Sebastian by the sea Florida

        88 Bayliner 21CC 2001 Mercury 225 HP EFI



        • #5
          Thanks for the replies. I still suspected it was a carb issue, but I wanted to double check. The coil and wires were replaced a few years. I replaced the plugs last year. I'll check the coil next time I have it on the water.


          • #6
            You should post as much technical info about your engine if you want help.
            For example, why don;t you tell us;

            what carburetor you have on the boat?

            Do you have aftermarket electronic ignition?

            How old is the gas?

            What is the timing set at?

            Is the timing advancing with RPM's?

            20' 1987 Renken Cuddy Cabin
            AQ131C 270 drive
            Southern NJ


            • #7
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              There is a plate with an arrow that goes between the carburetor and manifold, is it still there? If so then you need to be sure that all the tiny passages are clear.
              Kenner, Louisiana 1980 Donzi 18'. 2+3 6.2 MPI Alpha 1