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75 hp Suzuki 1986 DT 75 2 problems

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  • 75 hp Suzuki 1986 DT 75 2 problems

    This motor runs great between 1000 and 3000 rpms. It will not idle slow enough to dock or trailer without cutting off. Speed at 3000 rpms in my 16' McKee craft loaded or unloaded is 30mph. Motor alarms if I go above 3000 rpms or 30 mph. I have little to no outboard mechanical experience. My most urgent problem is with the idle. Once this problem is fixed I can work on the alarm. I appreciate any help with my motor problems. Thanks

  • #2
    Re: 75 hp Suzuki 1986 DT 75 2 problems

    Carbs have trash, will clean and see what happens with idler circuits.

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    • #3
      Re: 75 hp Suzuki 1986 DT 75 2 problems

      Been sorting through similar problems with a dt 85. Crutched idle problem by turning up idle speed slightly, will rebuild carbs over winter, probably has partially clogged passages as your seems to. Alarm situation is overheating. My alarm will consistently go off at 4000 RPMs. Have been sorting through this for months. Impeller seems to be #1 reason for overheating. This includes impeller, impeller housing and wear plate. Check these items first. Water bypass valve is a critical part of the water cooling system, as well as the thermostat. Timing affects cylinder head temps also. Do a thorough search on the archives here and you will find a wealth of information.
      Continue to post here, search here, lots of good folks/info here,
      Good luck, Larry

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      • #4
        Re: 75 hp Suzuki 1986 DT 75 2 problems

        Finished carbs, lots of black looking trash probably from fuel hose and bulb so those are replaced. Going on water tomorrow to verify if it is getting hot when it alarms. I will post results after this test. Sure hope it is not overheating. I would rather a bad sensor or some false alarm.

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        • #5
          Re: 75 hp Suzuki 1986 DT 75 2 problems

          Idles great. Alarm is still going off after running wot for 5 minutes. Engine temp was normal because I put my hands all around and did not feel anything hot while alarm was still going off. Oil level is good and oil usage seems normal. the oil level alarm does not work below 3000 rpms according to the manual. Is it just a level warning or could it work if not getting enough oil at higher rpms?

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          • #6
            Re: 75 hp Suzuki 1986 DT 75 2 problems

            So top speed is now 4500 rpms about 40mph on gps. I want to determine Which sensor (temp or oil level) is causing the buzzer to sound after 5 minutes at wot. How can I determine which one? Does anyone think it matters that top speed at wot before cleaning carbs was 30 (3000 rpms) after cleaning carbs it is 40 (4500 rpms) and the alarm comes on both times at wot for 5 minutes?

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            • #7
              Re: 75 hp Suzuki 1986 DT 75 2 problems

              WOT RPMs should be close to 5500, you still have a problem or it is over propped.

              Replace water pump and stat to start out with as they are normal preventative maintenance items

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              • #8
                Re: 75 hp Suzuki 1986 DT 75 2 problems

                Ok. Thanks I will replace the water pump and thermostat. How can I check the prop?

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                • #9
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                  Re: 75 hp Suzuki 1986 DT 75 2 problems

                  still waiting on thermostat and water pump kit to get here, but i drained most of the oil from tank and oil level indicator stayed the same as when it was full, ( 3 out of 4 lights on). Took boat out again and ran wot 30 minutes at 38 mph and 4500 rpms with no alarm. The prop is 19p same one that was on boat when it was running _>5500 rpms and 45 mph per gps.

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