Welcome Guest - Sign Up today
Welcome Guest - Sign Up today


No announcement yet.

Suzuki DT25C 1990 running problems

  • Filter
  • Time
  • Show
Clear All
new posts

  • Suzuki DT25C 1990 running problems

    Hello there chaps, my first post and posting from the UK.

    I just recently purchased this outboard and its been giving me a lot of trouble.
    The outboard wont idle and only runs on the choke, and isn't running on all 3 cylinders. Now normally when this happens I just clean the carbs+Jets and then they're running good as new (did the same on my Yamaha 15hp last week)

    I have stripped and cleaned the carbs and jets on this outboard twice now, using carb cleaner, compressed air and even ran Seafoam imported from the USA through it with no luck what so ever.

    All three plugs have a spark, all three cylinders have good compression, the fuel is perfect as there's a new filter on it with fresh fuel and also a brand new fuel tank and line.

    The outboard only runs with the choke on but not even on all 3 cylinders, and it also wont run fast either and not on all 3 cylinders.

    I ran it for 10 minutes or so with the seafoam in the fuel and then left to stand for 15 minutes and tried again with no difference afterwards.

    One more thing is that before all of this I put new plugs in which I checked after running the seafoam and the top cylinder plug was in great condition with no sign of fowling, the second cylinder was slightly wet and the third cylinder plug was very wet and oily.

    Do you have any suggestions?

    Im totally stuck as this is normally fixed just by cleaning the carbs and jets.
    It is a little confusing because the Idle/pilot Jet is at the top of the carb and the main jet in the float bowl (where they both are on my yamaha)

    Many thanks and I look forward to hearing from yourselves!

    Happy boating

  • #2
    Re: Suzuki DT25C 1990 running problems

    check compression and spark on all cylinders, then timing
    if all is well then work on fuel/air mix

    Too much fuel is just as bad as too little, cylinder will not fire properly

    Fuel pump leak will let too much into crank case of pulse port cylinder

    float setting maybe

    still problem with passages/jets maybe

    vacuum leak allowing too much air in is another thought


    • #3
      Re: Suzuki DT25C 1990 running problems

      Hi 99Yam40,

      Thank you for the response, I really appreciate any help I can get. I have no idea how I would check the timing as I thought it was all electronic. Would you be able to guide me on how to check the timing and correct if necessary?

      Also on this model Suzuki DT25C 1990 would someone be able to confirm if the mixture screw is (in for richer) or (out for richer)

      Thank you



      • #4
        Re: Suzuki DT25C 1990 running problems

        Timing light hooked to #1 plug wire just like an auto will show what the timing is doing,
        Just check to make sure it meets the specs in service manual.
        If it does not then it is time to look to see why

        Service manual for your motor will help you with all specs and procedures

        All adjustment screws I have seen on carbs of all kinds out was richer

        Still have not checked compression and spark?


        • #5
          Re: Suzuki DT25C 1990 running problems

          I have a Suzuki dt40 and went through these EXACT symptoms last year. After exhausting ideas at my skill level I took it to a professional. He had to adjust the float level a little but the main problem was, he said, BAD GAS. I had 2 week old premium gas with seafoam and startron in it. If you get bad gas with these small outboards, it's over. Try changing the gas.


          • #6
            Re: Suzuki DT25C 1990 running problems

            Mine also surges when I push in the choke in for a second or so and then shuts off. It also sneezes a lot but Im thinking the sneeze is because the top cylinder isn't getting enough fuel because the plug is so clean!

            I was a little cheeky and bought a compression tester today just to make sure all was well, i tested the compression and then took it back to the shop and they're not cheap!

            Compression Results:
            The top cylinder was just over 8bar
            The middle cylinder was just over 7bar
            The bottom cylinder was just over 8bar

            Is this considered good compression?

            All three cylinders have a spark, and im told that the ignition timing is electronic so once set never needs to be changed.

            Thank you for the reply Billten, Im not sure how the float can be adjusted, but im almost certain that it could be one of the problems on the top carb as the top plug is completely spotless compared to the bottom two.

            In the last 2 days I've put 2 fresh gallons of fuel through it with no difference to performance.

            Where do I go from here?



            • #7
              Re: Suzuki DT25C 1990 running problems

              So you have never checked timing to see if it is in spec even on you car?

              How many PSI is 8 and 7 Bar?
              Cylinders should be within 10% of each other

              sounds like what is called lean sneeze, not enough fuel.
              If you keep running a lean motor it will eat pistons

              Need to pull carbs and clean properly and set like service manual calls for.

              Pick up a manual and read up, if you do not think you can handle then take to a Suzuki shop


              • #8
                Re: Suzuki DT25C 1990 running problems

                top cylinder 120psi
                middle cylinder 105psi
                bottom cylinder 120psi

                No I have never checked the timing on anything, and dont have access to a timing light, nor do I know the specs that it should be.

                I agree with you that it is a lean sneeze as I don't believe that the top cylinder is getting any fuel as the plug still looks new, apart from the marks from where it has been sparking. The carb definately has fuel in it because when I opened the drain screw it came out and then refilled when I squeezed the bulb. It's just not getting from the carb to the plug.

                Ive got the carbs off again to have yet another clean etc.

                Other than the jets, could there be any other reason why the fuel isnt getting from the carb to the plug?
                9 times out of 10 it is the jets, but I want to know if there is any other possible reason, because they've been off and been cleaned out and blasted with compressed air 3 times now and I'm really starting to thing that they're not the problem.

                Once again I really appreciate your help and the time you've taken to reply.



                • #9
                  Sign up today
                  Re: Suzuki DT25C 1990 running problems

                  there are the main and pilot(idle)jets and then there are fuel and air jets, pilot adjustment screws and passages that plug.
                  Need to make sure to take carb completely apart and clean out all passages and readjust as manual calls for