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Runs Rough At Low Rpm

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  • Runs Rough At Low Rpm

    I have a 1985 Yamaha 150 HP, Model 150ETLK. I purchased this boat in January, restoring same.

    The engine will start and run, but rough at low rpms. When you lower the accessory throttle handle (703) and go to put in gear it will die.

    I have removed, cleaned and reinstalled gas tank. New line from tank to engine. New fuel pumps, gas lines leaving fuel pump are in great shape.

    I acted like wasn't running on all cylinders. Had to keep rpm's up some or it would die. I would estimate 1200 - 1500 RPM. When lowered to idling speed would die. I checked fire and I have fire on all 6 cylinders and the compression is: 110, 110, 110 on L Bank and 110, 105, 105 or R. Bank.

    Removed carburators and disassembled.

    Thanks
    Jim
    Diana, Texas

    Top: Clean as a whistle, but tore down, sprayed all jets and passageways with Carb cleaner, blew out and reassembled.

    Middle: Same as top, but with just a little varnish in the very bottom of bowl. Performed same operations as above.

    Bottom: Had a lot of white jelly like stuff throughoutt bottom of carb.
    Cleaned thoroughly. A little pitting in bowl, but nowhere else. Float and needle operate great. Cleaned all jets a passageways.

    All air adjustment on all carbs was set a 1 1/4 turns out.

    Reinstalled, runs somewhat better, but still dies when you approach idle.

    Started and ran while spraying carb out in each barrel of each carb. Some barrels it made no difference except maybe to lug engine a little. Two of the barrels, I think, it would rev up when I sprayed it. Sounds like those particular ones are not getting enough fuel.

    I opened up the throttle just momentairly to high speed and it sounded like it would get it.

    I did not look at reeds.

    This engine had set for seven years. I did a carb out earlier and then installed new plugs. I was preparing to take to lake for initial run, but decided to check it out further. Glad I did.

    Can anyone give me any suggestions. I am thinking about takeing the carbs off, again, ordering a repair kit and re-cleaning them.l All of the throttle bodies, throats, etc. are in nearly perfect shape.

    The numbers for the carbs are: 64G-14301, 14302, 14303. These carbs are obsolete now. I hope they can be overhauled.

    Any suggestions or advise would be appreciated.

  • #2
    Sounds like the low speed jets in bowl of carb is plugged up, hold bowl up to light to see if see light through jets.
    Regards
    Boats.net
    Yamaha Outboard Parts

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    • #3
      Are the low speed jets the ones in the front that point forward?

      Thanks
      Jim
      Diana, Texas

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      • #4
        They are in bowl, under small screw in bottom of bowl.
        Regards
        Boats.net
        Yamaha Outboard Parts

        Comment


        • #5
          Thank you, I will look for them. I did not see them during the initial cleaning. However, I wasn't looking for them.

          Thanks, again.

          Jim
          Diana, Texas

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