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  1. #1

    250 Ultra vs 15F ... why ???

    Ok, I'm not a mechanic, just a jet ski owner, and many of you gear heads will be rolling your eyes at this post, but I am trying to learn something here, so at least give me credit for that

    So how in the hell is it that my 04' 15F does around 62 mph stock with 160 HP and around 900 lbs of thrust, and my 08' 250 Ultra does around 67 mph with 250 HP and around 1600 lbs of thrust ? It is no where near proportional ? I grew up sailing, so I know that you are a slave of your hull to some extent, but that can not explain the delta. I guess it must be electronically limited , but why doesn't Riva or somebody smarter develop a chip or ECU that resolves this ? I mean I see all these external mods like exhaust, intakes, impellers, super charger improvements, blah, blah, blah ... why all of these physical mods ? Must just be software ? Seems to me 250 ponies should be able to push the 250 a whole heck of alot faster than my 15F ... do we really need another 90 horse to increase top end 5-6 mph ? Why not just add a larger pump and larger impeller to the 250 ... push more water out the back ... is that the issue ? I have a BMW with Dinan software that removes the top end limiter, advances timing, modifies the torue curve, and allows the rpm's to climb much higher, among other things ... does this exist for the 15F or 250 ... this seems alot easier, less expensive, and much smarter than bolting on all this aftermarket stuff to make it breath better. Seems like the HP is already there, it's just not being maximized. Please educate me.


  2. #2
    Formerly Ultra250 TN Aquaholic6801's Avatar
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    Quote Originally Posted by Skaneateles 08 Ultra 250 View Post
    Ok, I'm not a mechanic, just a jet ski owner, and many of you gear heads will be rolling your eyes at this post, but I am trying to learn something here, so at least give me credit for that

    So how in the hell is it that my 04' 15F does around 62 mph stock with 160 HP and around 900 lbs of thrust, and my 08' 250 Ultra does around 67 mph with 250 HP and around 1600 lbs of thrust ? It is no where near proportional ? I grew up sailing, so I know that you are a slave of your hull to some extent, but that can not explain the delta. I guess it must be electronically limited , but why doesn't Riva or somebody smarter develop a chip or ECU that resolves this ? I mean I see all these external mods like exhaust, intakes, impellers, super charger improvements, blah, blah, blah ... why all of these physical mods ? Must just be software ? Seems to me 250 ponies should be able to push the 250 a whole heck of alot faster than my 15F ... do we really need another 90 horse to increase top end 5-6 mph ? Why not just add a larger pump and larger impeller to the 250 ... push more water out the back ... is that the issue ? I have a BMW with Dinan software that removes the top end limiter, advances timing, modifies the torue curve, and allows the rpm's to climb much higher, among other things ... does this exist for the 15F or 250 ... this seems alot easier, less expensive, and much smarter than bolting on all this aftermarket stuff to make it breath better. Seems like the HP is already there, it's just not being maximized. Please educate me.
    OK first of all 160hp (@ 750 lbs) vs 250hp(@950 lbs) second Ultra is @11" longer, (more wetted surface), 3rd the 250 hull is made to handle rough water..............also the Roots style supercharger is geared more to low and midrange..........

  3. #3

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    You are fat.

  4. #4
    jtskir15f's Avatar
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    Quote Originally Posted by eel View Post
    You are fat.


    adding a bigger pump or throwing a steeper impeller at it wouldnt do anything, because right now even with all the parts out, i dont think anyone is running enough power to make a bigger pump doable. it would take a lot more power to make a bigger pump work. and it takes a lot more to go fast on water compared to goin fast on land.

  5. #5
    Flat water sucks! yz426er's Avatar
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    Quote Originally Posted by eel View Post
    You are fat.
    Dont be a d!ck.

    The 15f is so much lighter and flatter on the bottom. Definately a "slave to the hull". I love the feeling of the 15f when it get's a bit rough, just keep er' pinned and hang on. The 250 is "nice" to ride if you are into that "planted" cut thru the water type feeling. I prefer a lot more action

  6. #6
    Ok, let me address you guys-

    Ultra 250 Tn, go to the Kawasaki website to see their 250 Ultra published specs.

    Maximum Thrust1,524 lb



    I copied and pasted the thrust from the 250 just to make a quick point, but go research yourself

    http://www.kawasaki.com/Products/det...specifications

    Maximum Thrust on the 15F is 957 lb... so both my estimates were correct.

    C'mon man, you post alot on this board, keep your street-cred up

    All of you are missing my point though ... 250 HP should be able to push a bath tub down a smooth lake at 75 mph plus. Forget about the 250 and 15F comparison, compare the 250 Ultra with it's 250 horse to any other 4 stroke ski that is in the 60+ mph range ... it just seems like the 250 should be faster ... we can talk hulls all day but it should not take 90 horse to push the 250 5-6 mph faster than the 15F ... I have to believe the Ultra LX with the 160 ponies does 60'ish ... see my point ? If 160 HP can push that hull 60 'ish , seems like 250 HP should push it alot faster. There is some limiting factor on the 250 and it seems like electronics play a big roll ??? Like I said, not a mechanic or hull design engineer or physicist ... I'm just trying to wrap my brain around this using some common sense.

    eel-

    I would appreciate your comment "that I am fat" if it were true or funny or witty or tied in to the thread in any meaningful way, but it does not. So you know, I'm 6'1" 230 former Marine, show some respect kid. Just remember, when you were down in the shop wing in high school learning about combustion engines and smoking cigarettes in the boys room, dreaming about changing somebody's oil at your after school part time quick-lube job, I was in AP Social Studies class thinking about the varsity football game I would be playing in later that day and where I was going to go to college... I'll stop here, too easy to beat down a simple form of life like you. Now come back and tell me how you are a rocket scientist and played quarterback for the 49'ers and now you sleep in a bed full of 100 dollar bills with all your ladies


    Jtskir15f - Thank you, point taken

    yz426er- I have not ridden my 250 yet, sitting in the lift waiting for me ... I live in SF and it is at my NY lake house ... look forward to comparing to the 15F that just had the Riva rpm kit installed, less a rideplate since they can not seem to ship one right now. I still question that the hull can make this big of a difference ... affect it yes ... but the numbers are so far out of whack in terms of HP vs top end. Looking forward to more feedback.

  7. #7
    inchadeboca's Avatar
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  8. #8
    Formerly Ultra250 TN Aquaholic6801's Avatar
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    The Ultra LX runs in the low to mid 50's like 53 to 55 mph (gps) stock, so thats 12 to 13 mph with 90 extra hp.......................

  9. #9
    OK Scan, now that was funny. But anyway back to the point, I've often wondered about the huge discrepancey between HP and speed. I mean 90 more HP and only 5 mph. difference? Don't seem right to me. Could it be that they're governing the thing?

  10. #10
    My Jet Ski drinks more than yours Glenozzy's Avatar
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    I'm 6'1" 230lb
    nope your still fat

    I am 6'2" 230 and my doctor tell me I am fat

    so welcome to the club

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