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  1. #1

    help with seadoo 951 jetting

    A background on what is going on. 2 years ago bought the ski and put about 10 hours on it when the engine blew up due to lack of oil. replaced engine last year with an sbt engine and also rebuilt the carbs. ski starts and runs great out of water, when in water the ski will die around 2000-2500 rpm at 75% throttle or less unless you pull the choke out an feather until higher rpm. if you give it full throttle at idle ski takes off no bog, sputter, or die. when you are driving the ski and then let off the throttle to slow down if you dont feather the gas the ski will die but start right back up. i have played with the hi and low speed jets to try to solve this problehem i currently have the low speed jets almost all the way out and the high speed jets 1/2 turn out . there was also some water leaking from plastic exhaust resnator so i bypassed and installed a free flow exhaust ( could this cause engine to run lean or cause this problem?) also i do not have the airbox installed that way i can get access to the carbs easier ( which can also cause a lean condition?) accl pump squirts very good on pto side it sprays ok not great on the mag side i have replaced the fuel lines. I do not want to run the ski to much as i dont want to blow it up i did adjust any pop off not sure if this could cause this? thinking jetting would be the answer ? any help would be much appriciated if jetting is the cure which size jets should i try Thanks!

  2. #2
    If i knew,...I wouldn't ask sea-one's Avatar
    Join Date
    Aug 2009
    1st, what model ski? Whats you max RPM?
    Also are the JETS stock?
    Exhaust change like that shouldn't effect a "Lean" issue HOWEVER....Its known that at 3/4 throttle is at it's most Leanest condition, It's a phenomenon as it's been called.
    You read your plugs? They need to ideally be a Chocolaty color electrode and oily on the thread rim....
    ALSO with the Stock air box OFF it totally changes the "pop-off" pressure.The transition from LOW speed jet to the HIGH speed jet.
    So if your going to run the stock air box then unfortunately to get a proper tune you need the stock box on it...
    As for the Jet Screw settings?,,,, The LOW screw is only for IDLE tune only..1.25 to 1.5 is all it should be set at, The HIGH screws?... I've run them at all settings but anything after 3 turns out is all you have with THAT JET you have in the carbs.
    REMEMBER the previous motor blew so i hope the issue was found and corrected at the time of the NEW motor?

    So put the airbox on , button it up like it should be and go from there.
    But IN MY OPINION? Set the LOW speed at 1.5 out and the High speed screw at 1.0 out , put the airbox on it to correct the 'pop-off', Ride it if you think its safe for the motor, read the plugs after a WOT run . Chop the throttle, Shut it down (off), Take a wrench with you to check them on the water. READ the Plugs... WET? or are they DRY? ..
    Im at approx 500ft above sea level for these settings, i can't see where you're at to offer anymore advice and do not claim this info to be good for you , but after years with carbs and tuning with Rossier perfomance mods this is what i've learned over time with their help. Those we're the days of simple fun and quick little beastie skis without all the bureaucratic bs.

    goodluck and keep us updated


  3. #3
    wkuadam07's Avatar
    Join Date
    Feb 2013
    Bowling Green, KY
    You have carb issues. Pop off setting is critical. Read one of the many mikuni carb threads and take all that good advice to heart... if all else fails on the carbs send them to an expert.

  4. #4
    njrealtor55's Avatar
    Join Date
    Dec 2006
    Flemington, NJ
    send your carbs to chris at watercraft majic for cleaning/adjustment. then reinstall with the airbox. if you are not careful you can blow up your engine, or have it run away when out of the water

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