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Thread: xr 1800

  1. #1

    xr 1800

    I know this isnt the jet boat section but I get a lot more info from the ski guys anyway so here my situation
    First a little history......rebuilt not cleaned all 6 carbs... installed rejet kit from island racing. d-plate,riva flame arrestors solas props 13/19.... premix.plugs pinned..wave eater clips and couplings...compression on all six about 110 psi average all six plugs show golden brown after full throttle runs both engins turn about 7100 rpm. both feel good at idle and response well 4000k bog completlty eliminated...the only problem I have is that one engine gets to full rpm a 2-3 seconds faster than the other one almost feel sluggish not as crisp or responsive as the other engine. my low speed adjust is at 1.25 out and my high speed is at 1 and a half out on all carbs i double checked everything... any ideas or help...Thanks

  2. #2

    Join Date
    Sep 2007
    Lexington, Ky
    Typical of a twin engine jet boat that does not have counter rotating props. Because of the angle the water enters the tunnel, and the fact that both props are spinning the same direction, one side is going to be more effecient than the other. If they were counter rotating then they would load evenly. One prop has its leading edge pointing into the incoming water stream, while the other side has its leading edge against the flow of the water into the jet, this allows one side to grab the water better than the other, make sense? Of course there could be an issue with one of the engines causing this, but based on your description, I would say there's a 99% chance this is the cause for the problem you describe. Most everyone I've talked to runs a different pitch prop on each side in an attemmpt to compensate for this. Otherwise, as you've stated, one engine will have to have more throttle than the other to maintan the same RPM's on both engines while crusing.

  3. #3
    true but both motors used to perform equally. i only notice it would turn better to the left than to the right kind of like torque steer. but this feel like a smal l bog so i suspect I missed something when I rebuilt the carbs or i am not tuning that motor correct. thanks for your input. any other suggestions

  4. #4

    Join Date
    Sep 2005
    Caroline , VA
    If you think you missed something in the carb rebuild, switch teh Carb racks from one engine to the other.

    I sold my XR last june, and one engine always revved quicker and around 75 rpms higher . 54 on GPS was the best speed I ever saw.

    Make sure the reverse gates are not hanging into the exit nozzles.

  5. #5

    Thanks for the info

  6. #6
    vomitspot's Avatar
    Join Date
    Apr 2006
    mobile alabama
    dont alway rely on the oem tachs , not the most accurate

  7. #7
    32 Valves To Love! Racecar_Dave's Avatar
    Join Date
    Jul 2009
    Alum Creek
    Whats your boat gps-ing at? I wonder if you could throw two sets of triples on!

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