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90hp rough running - then fine?

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  • 90hp rough running - then fine?

    On a 1989 90hp ETLF -For the last 8 years the boat was used 150 plus days a year. But this problem did start after the boat was unused for 3 months. The type of use requires short runs of 3 - 10 minutes, engine off for 15 - 20 minutes, then repeat. Usually happens like this. Engine runs fine and restarts fine for the first couple of hours. Then starts easily and idles fine, but upon asking for power engine raises rpms to 1500 plus (or so, I'm guessing) but is extremely rough running and will not get up and go. But, if you let it run rough for a minute or so, it will all of a sudden run fine again. It's done this 3 times. I got the boat out of the water within minutes each time. After the first time, I pulled the carbs and cleaned them, but have not rebuilt them. It seems like it might be a needle valve sticking closed? All I've ever done to this engine is yearly plugs, filters, etc. , it's been a great engine!! I welcome you imput. Thanks!

  • #2
    Run a compression test to see if all cylinders are even. Check for spark on all cylinders when engine running rough with a timing light to see all cylinders are firing. Carbs need to be throughly cleaned, check fuel pump and fuel filters.
    Regards
    Boats.net
    Yamaha Outboard Parts

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    • #3
      While you have the timing light hooked up, check the timing to see if it is advancing properly while restricted RPM.

      Do you have gauges that would indicate any alarms?
      Check alarm system to make sure that is functioning properly, you may have something setting it off but buzzer is not working

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