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  1. #1

    Unhappy Setting High speed

    I have an SL 780 and it really bogs in the lower RPM. When I try and get going I have to almost give it full throttle to take off. But when it takes off, it really goes. I wanted to make sure the low and high speed adjusters were at factory settings. The manual said 5/8 on low and 7/8-1 on high. My problem in I can't figure out which adjuster on the carb in which??? There is one with a T head that turns fine and one with a blade that only sweeps 60 degrees. The blade one can't adjust far enough to be a proper adjuster and then where is the other one??? Does anyone know of a picture of this carb with arrows and labels to the adjusters.

    Thanks, this has been frustrating to figure out...


  2. #2
    thester71's Avatar
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    Quote Originally Posted by dfreadhoff View Post
    I have an SL 780 and it really bogs in the lower RPM. When I try and get going I have to almost give it full throttle to take off. But when it takes off, it really goes. I wanted to make sure the low and high speed adjusters were at factory settings. The manual said 5/8 on low and 7/8-1 on high. My problem in I can't figure out which adjuster on the carb in which??? There is one with a T head that turns fine and one with a blade that only sweeps 60 degrees. The blade one can't adjust far enough to be a proper adjuster and then where is the other one??? Does anyone know of a picture of this carb with arrows and labels to the adjusters.

    Thanks, this has been frustrating to figure out...
    The ones with the "blades" are your high speed adjusters, those are limiter caps and they come right off with a pair of needle nose pliers, make sure you read up on tuning carbs before you start messing with the highs. The t handles are your low speed adjusters, and finally the other one on the mag end is your idle adjuster. Turning the needles out (counterclockwise) increases fuel flow, and obviously turning them in(clockwise) decreases fuel flow

  3. #3
    Thanks! I was playing with the "low" speed yesterday and turning them in a quarter or out a quarter didn't seem to change the bogging nature. What options do I have now???

    Thanks for any help.

  4. #4
    The low needle is just an idle mix. Anything past the first bypass opening is the pilot jet. (for the most part) Sounds to me like.....


    1) the bypass holes in the carbs are plugged up.

    2) the pop-off pressure is wrong.

    3) you have an air leak in the intake.

    4) fouled spark plugs

    Or

    5) Your compression is low.



    This is all assuming you are jetted correctly in the first place.

  5. #5
    One more thought... if your reeds are getting weak, they may not be sealing at low RPM's.

  6. #6
    la90043's Avatar
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    different year model of your SL780 not only have different low and high jets internally but also have different low speed and high speed adjustments on the screws.

    What year is your boat huh?

  7. #7
    1996. I was given the carbs and manifold off of a 1996 SLX. Is it possible to put these on and increase my performance?

  8. #8
    While I was adjusting the carbs, I found a small rod that comes up from below. it looked like it should be attached to the throttle block. I put it back on. I am assuming this is the variable control on either the fuel or oil pump. Can anyone tell me which and what if any problems I will have because this wasn't attached to anything???

  9. #9
    la90043's Avatar
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    these settings are for the 1996 SL780

    high speed screw are mag=3/4 ctr=3/4 pto=1

    low speed screw on all 3 are 5/8

    As for the extra carb you have off a SLX780 the jets are different and the turns on the screws are different. it wont increase performance. it will make the boat untunable though. they both have the same carb. The Mikuni SBN but with different jets and screw settings.

    as for the rod. its the oil pump rod. as throttle is increased so is the volume of oil to the engine is increased. when the rod is disconnected the oil pump goes to fully open. meaning the maximum amount of oil was always being given to the motor. its a fail/safe system on the pump. now thats its connected it'll probably smoke alot less and the engine will be given the volume of oil thats required per throttle position.

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