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The Johnson 50 hp "Bog Down" issue......

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  • The Johnson 50 hp "Bog Down" issue......

    I have read a lot of post and got some good ideas..But,,I have been grappling with this issue: 1989 50 hp Johnson: After warming up a little. Motor just bogs down like a fuel starvation problem, but i dont think it is that. I have had this problem for several seasons, this is what i have dont.
    Carbs do not have high speed jets. I have put about 4 kits in. Carbs are clean. Fuel is clean. I took tank apart, flushed, cleaned pick up line, new filters. Replaced VRO ($$), changed gas lines, took choke/primer apart..replace membrane,seems fine. Last year I placed bulb vertical that seem to fix it, but still acting up. Compression check is 120 and 115 psi. Replaced water gasket, impellor, some lower end bushings, prop, when i got the boat several years ago. Motor is "peeing" strong, new plugs every season, test fire by placing plugs on block, turning over, fires looks strong, capictors on stator are hermatically sealed, looks brand new. A boat shop checked coil and charge, said it was strong and coils just go out -not a evolving failure. However, I saw a post where someone replaced the coils with a
    similar problem and ran good afterwards.....
    Can coils semi fail, or do they just peter out ?
    I also saw a post where a guy activated his choke while bogging down and it ran better ?? I suspected my choke primer, but it clicks and is very clean inside, i did replace the membrane/gasket. Right now i disconnected oil from VRO, going manual mix, because i thought too much oil was gettin in causing a fouling, i thot this because oil was accumulating in the air silencer when motor is tilted for storing......Im thinking coils...Motor usually kicks right off, i have to let it idle and warm up @ 5 minutes , usually runs great, now it idles a little rough, takes a few more starts to idle,,,,,shop said coils were fine,,,but they are 1989 year......and only shop within 200 miles..... please through me your ideas !


  • #2
    Re: The Johnson 50 hp "Bog Down" issue......

    There is a jet (little replaceable brass orifice) that sits in the bowl, behind the drain plug. Isn't that technically your high speed jet? I believe it limits the speed at which the gas flows up the feed tube.

    I would pull it and make sure it's clean.

    Obviously you are losing power when you nail it, as you said bogging down.
    Is it consistent or popping down?

    Fuel pump? If the fuel pump was not able to keep up with your carbs, that would cause it to bog down.

    I don't buy the coil. If you checked it on your meter and it read good, it's good.

    I have a 50VRO, 1992, so I have been through my own personal hell.
    Never bogged down on high end though, always low end.

    Comment



    • #3
      Re: The Johnson 50 hp "Bog Down" issue......

      the manual says this model has no high speed jets, - but yes there are jets behind the drain plugs, i have checked them many times, looks brand new, I suspected that also, is why I flushed and dismantled the gas tank. After it warms up, the loss of power feels like if you pull the throttle back. It runs about half or more throttle. This last time out, at about 2/3 throttle it would cut in and out, same thing at WOT, jerking sort of.. Reason keeps saying fuel starving, but I have checked everything fule wise several times............hole in cap, bulb, air leaks, new hoses,,,the reeds behind the carbs look brand new also, last time it started I was pulling my kid up out of the water on a wake board, the 50 will get em up fine but was pulling a lot of drag at first, then started cutting out....however, this problem existed way before we started using the wake board......in the beginning of summer, this thing would fly across the water, now I woudl like to find out if the voltage to the VRO is mal functioning, maybe if a loss of voltage is causing the VRO not to operate properly, " maybe heat causing loss of voltage,,,,,I wonder how the vro is fed electrical wise.........

      Comment



      • #4
        Re: The Johnson 50 hp "Bog Down" issue......

        Have you ever actually cleaned the jets in the bottom of the float bowl?

        You need to actually run a stranded copper wire through them to get them clean, they can look clean and not be.

        Chased a similar problem, replaced coil and CDI then cleaned the carb correctly(3rd time) and it ran like a top so try that, it is easy to do and free and it may just fix your problem, if you haven't run a wire through them they aren't clean.
        GO IRISH!!!!

        Comment



        • #5
          Re: The Johnson 50 hp "Bog Down" issue......

          i had the same issue on my 1985 50hp. my top cylinder wasnt sparking. i ended up pulling the bottom plug and wire and moved them to the top cylinder and top coil. after i did that there was spark. so i put the top plug and wire on the bottom cylinder and bottom coil and ther was still spark. so the only thing i can think of was that i had a bad connection with the top spark plug wire and the top coil because now i have spark in both cylinders.

          Comment



          • #6
            Re: The Johnson 50 hp "Bog Down" issue......

            what year motor?

            VRO is vacuum-operated, voltage is not an issue.

            is your tank vent open and clear?

            An ignition coil might fail suddenly all at once, or it might start failing intermittently before it goes completely dark.

            Use an inline spark tester (couple bucks at autozone), set the gap for 7/16", clip it to the engine block, attach the plug leads (one at a time) and look for a strong blue spark while cranking. If it can't jump a half-inch gap in the open air without a spark plug, it's not firing in the hole under heat & compression. not consistently anyway.

            Inspect the wires coming off the timer base, look for burnt/chafed/missing insulation, where a bare wire might contact or arc to ground when throttle is advanced.

            [FWIW, I have found the terminology in the manuals to be inconsistent year to year, and even within the same manual...I've always referred to those orifices as "jets" anyway....]
            It's all about the tools.

            "If the ocean is glass flat and the sun is shining, you open up the special memory compartment of your brain and start recording the smells, sounds, sights and feelings." -- Philster

            "Poets talk about 'spots of time,' but it is really fishermen who experience eternity compressed into a moment. No one can tell what a spot of time is until suddenly the whole world is a fish and the fish is gone. I shall remember that son of a b**** forever." -- N. Maclean

            Comment



            • #7
              Re: The Johnson 50 hp "Bog Down" issue......

              Hey guys. First time user, having "bogging down issue" with my 1986 50HP Evinrude too.

              Getting good spark, replaced primer solenoid, took apart carbs and they are very clean in the main chamber areas. Engine idles with a bit of "jerking" and won't confidently run at low speeds (makes docking boat parallel in the lagoon a real pain) also bogs at WOT (like starved fo fuel). If I manually move that red lever to the rear position on the primer solenoid it will run WOT fine but then stall out when reduce throttle. I read all the stuff related to what this solenoid does and think I get why using this manual adjustment works at WOT.

              Timing? Not idling smoothly or at low speed might be timing right? But would timing be an issue if I can get it to run ok at WOT with this manual adjustment?

              Carbs? Should I take carbs completely apart (I have seen this small brass orifice/jet being refered to in the float bowl area) and clean again?

              Great forum, been quite informative so far.

              Comment



              • #8
                Re: The Johnson 50 hp "Bog Down" issue......

                weylthing, welcome to iboats.

                it gets confusing trying to fix two motors in the same thread, so pls start a thread of your own. thx.
                It's all about the tools.

                "If the ocean is glass flat and the sun is shining, you open up the special memory compartment of your brain and start recording the smells, sounds, sights and feelings." -- Philster

                "Poets talk about 'spots of time,' but it is really fishermen who experience eternity compressed into a moment. No one can tell what a spot of time is until suddenly the whole world is a fish and the fish is gone. I shall remember that son of a b**** forever." -- N. Maclean

                Comment



                • #9
                  Re: The Johnson 50 hp "Bog Down" issue......

                  he he, yeah it can get confusing alright....nonetheless...Yes,I have had the jets out, sprayed carb with cleaner, run wire through them,blowing them out with air compressor. The floats and seat seats seem fine, no leaks there, I have re kit the carbs about 4 times. You are right on the VRO, is only vacuum operated. I did replace the VRO couple of season ago, b/c i thot that was a problem, now I have 2 vros. But back to this coil suspicion...I see there is still this debate about "if they can intermitantly peter out" or just blow, I tend to believe that they can as heat and electrical do not go well together. The other advisor says to switch the coils as a check, I think i did a few seasons ago, but that brings up a thought, to pull the wire while running, (even though i have good spark), to see if it changes......when i checked compression, I hit the starter @ 3 seconds and top was 120psi, then for the bottom, I hit the starter for 2 sec and only read 109 psi, hit it again for about 4 seconds and it reads 116 psi. -that is on a cold motor,,,,I have a spark plug wire tester bulb, to check for spark while running, its fine standing behind the engine, but I havent stood there ripping down the lake,,,,I assume the spark gap tester is a different device, Will that tell me if the coil is still up to par depending on the spark's ability to jump the 7/16 or so ???

                  I really dont think it is a fule problem, for i have been thru the fule deliema many times....however, if the VRO runs on cyl #2,(i dont know which one) and it is malafunctioning, it may be affecting the pulse psi........previously the motor always kicked off on 1st or 2nd try and idled perfect (keeping in mind these bogging down issue has been exisiting) the motor just began to IDLE rough on last venture when this bogging down began (i.e. again) -like a miss,,,, thanks everyone for the thoughts,

                  Comment



                  • #10
                    Re: The Johnson 50 hp "Bog Down" issue......

                    On the compression test, I always run the starter 3 times for a couple seconds. The highest PSI you can get to is the relevant number. I have heard that those preliminary numbers tell a story, the rate at which it builds up to its top reading, but for all I know those are just rumors. I don't know how much PSI is required to run the pump, but if it's not keeping the carb bowls full for any reason (including inadequate vacuum), the bulb would be soft when you shut the motor off.

                    Swapping coils is great when you know which cylinder has no spark; in this case I don't see how it would rule anything out.

                    About the spark tester...I know a bad coil can't push a spark across a half-inch gap...I don't know how those light bulb testers are calibrated...it might just be a "spark/no spark" test, without indicating quality of spark.

                    You can also test the coils with an ohmmeter. Resistance specs are published in the troubleshooting guide at www.outboardignition.com
                    It's all about the tools.

                    "If the ocean is glass flat and the sun is shining, you open up the special memory compartment of your brain and start recording the smells, sounds, sights and feelings." -- Philster

                    "Poets talk about 'spots of time,' but it is really fishermen who experience eternity compressed into a moment. No one can tell what a spot of time is until suddenly the whole world is a fish and the fish is gone. I shall remember that son of a b**** forever." -- N. Maclean

                    Comment

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