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1993 Yamaha 25 hp 2 stroke carb/throttle issue

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  • 1993 Yamaha 25 hp 2 stroke carb/throttle issue

    Here's another one for you guys. As indicated in my last thread, water pump is working great. Took the boat out to run yesterday and she won't accelerate at full throttle. Engine sounds very deep and boggy. I couldn't even get boat on plane....and the boat is '14 fiber, very light!! When i back off throttle then quickly throttle up, there's a delay in response too. I dont have a rpm gauge but im getting is 1500-2000 max. Now I think about it, when flushing on muffs and throttle up in neutral there is delay too. Gota be the carbs, right?

    Fuel/oil mix is new and so is fuel filter, tank, bulb, and line. Engine is definitely getting fuel. Sounds as if its too rich. This engine did sit in the backyard of the prior owner for 4-6 months. Im certain the carbs need cleaning and adjusting, obviuosly. But is there something else Im missing? Im definitely an amateur when it comes to carbs. But ive read the adjustment isn't difficult. Can you suggest an article/website with carb adjustment sequence. I recall reading you close both (2 carbs) adjustment screws all way closed, then begin opening 1/2 turn until you get clean idle. Also, is the timing/seeking involved? What should I know about adjusting this? Thanks in advance!
    Jason
    1998 S115TLRW + 1976 Aquasport 170

  • #2
    Kind of sounds like you have not got your hands on a Yamaha Service Manual for your motor yet.

    Get one it will help you and save you lots of time trying to get info you are needing.
    If you do not understand something in the manual you can ask even more questions.

    After cleaning carbs and reinstalling you will need to follow the link and sync procedure in manual if there is more than one carb.
    Set the pilot screws to the spec listed in manual and it should run well in the +or - tolerance they give for the spec. If it does not there is a problem with the carb or something else on the motor

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    • #3
      I do have Clymer's repair service manual. It covers my make/model but the entire manual isn't specific to my model. More of a general book. Is this what you're referring to? Ive looked online for an orginal service manual with no success.
      Jason
      1998 S115TLRW + 1976 Aquasport 170

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      • #4
        ...and this manual covers disassembly, cleaning, and assembly of carburetor. It does not cover adjustment/tuning.
        Jason
        1998 S115TLRW + 1976 Aquasport 170

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        • #5
          http://www.yamahapubs.com/index.do?pg=search&category=4

          You should be able to find the correct # here.
          and then do some searching for one on the web
          YAMAHA MANUAL STORE

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          • #6
            I'll check it out. Thank you and happy 4th!
            Jason
            1998 S115TLRW + 1976 Aquasport 170

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