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  1. #1

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    How accurate is stock speedometer?

    I just purchased a stock 07'ultra 250 with 28 hrs.on it. I am trying to figure out if my ski is running up to par on the top end. I am 6'5 about 300 pounds and with a half tank of gas only getting 60 mph out of ski.The rpm's are around 7720-7740 and getting 11 lbs. of boost. I have done my first oil change and pulled out a littie over 4 1/2 quarts of oil; not sure if it's GIO or just an over fill from the 10 hour service. But I will monitor it for sure!!!! Any ideas would greatly be appreciated!!!!!!!
    Last edited by rworthington; 06-25-2009 at 06:38 PM. Reason: Borrowed a gps and got 59 mph on the top speed with ideal conditions,so now I am curious my ski is not up to speed?


  2. #2
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    get a gps..only way to know for sure what you've got. From what I've seen, most speedos ( cars included) are relative to lots of outside factors.

    A garmin map 76 will set you back about 100..it floats and is a good unit..you can run it off a 12v feed on your ski too.

  3. #3

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    Mar 2008
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    I have gps'ed my 15f and found the speedometer is off about 3 mph on the top end , just cruisin ... its pretty accurate depending on water conditions. Your ski could be off that much or possibily more .. Just need to get a gps and find out. The gps unit that nmpeter refered to is a excellent choice , I have one myself. Stash it in the storage compartment and take a ride. It has a memory so you can do a few runs come back and average them out and see what you have.

  4. #4
    Erikfar Erikfar's Avatar
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    Oct 2008
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    Clearwater, FL
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    Even with the inaccuracy, you should be seeing more that 60 MPH

  5. #5

    Need more info

    Your top speed depends on a lot of factors. Here are some:

    Water Conditions
    Wind Speeds
    Wind Direction
    Temperature
    Elevation
    Gas Type (make sure you use 93 octane)
    Rider Weight (you are a pretty big guy)
    Rider Posture (superman position vs sitting normally)

    If you could tell us some of this info it would be easier for us to tell you if 60mph is reasonable.

    Personally, once when riding on my stock 250x, on a day when all of the above conditions were ideal, w/ me riding superman position (and being my wimpy 155lb self) I hit 70mph on speedometer. I would say I average 65-67mph at WOT according to speedometer (which as it has been said is inaccurate).

  6. #6
    robk's Avatar
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    My spedo on my 15F read 70 when the garmin read 64.7

  7. #7
    gary's Avatar
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    i have an 08 ultra 250x it reads 70 some days and 65 some days,my gps speed is always in the 67mph range though.like everyone else says,get a gps,the only way you will know your actual speed.

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