Page 1 of 2 1 2 LastLast
Results 1 to 10 of 16

Thread: speed vs hp

  1. #1
    home of the dislexic fingers breon's Avatar
    Join Date
    Aug 2007
    Location
    port st lucie fl
    Posts
    3,471

    speed vs hp

    in 98 or 99 my sister hat a 3 seater yamha at 130 hp it ran along at @ 60 now 10 years later the new skis are over 100 hp more and they are only going 10 mph faster... .????? now the rxp 215 goes @70 out of the box and the rxp x is 40 hp more is it still going to do 70 or is it going to be like the cars were in the 80's where the speedos only went to 85 eventhough most would do over 100.. the us coast guard has some ruling on the 70 speedo thing i think ... i just insured my ski and they ask if it went over 70... i'll never tell r they just going to make the nozel big enough to make it only do 70 and just make more acceleration with the extra power any thoughts
    Last edited by MikeTrin; 10-08-2007 at 10:28 AM.


  2. #2
    Two things:

    One, it takes a LOT of power to go fast on water. Water is much, much denser than air. Taking a given hull design, it only takes a small amount of HP to reach a certain speed (say 50-60 MPH) and then LOTS more to get every MPH after that. This is why you see guys on here adding an intercooler and a high boost wheel, for example, and only picking up 2 MPH.

    Two, the PWC manufacturers have an unspoken agreement with the US Coast Guard to keep speeds around or under 70 MPH. The RXP-X would be capable of more speed, but if you read the 2008 Discussion thread you'll learn that Seadoo has made several design changes targetted specifically at keeping speeds down.

  3. #3
    Chrisrokc's Avatar
    Join Date
    Apr 2006
    Location
    Oklahoma City, OK
    Posts
    3,667
    Another good point is that the RXP hull isn't very "speed" friendly when compared to other hulls such as the GPR hull. You will see the RXP motors in GPRs running in the 80's with everything mostly stock.

    I am in the process of doing a big bore kit on my GPR. I am told hp wise from members of this fine forum I will have around 200hp, maybe more. Speed wise though I will have 81+mph if setup correctly.

  4. #4
    home of the dislexic fingers breon's Avatar
    Join Date
    Aug 2007
    Location
    port st lucie fl
    Posts
    3,471
    so... if the rxp hull isnt speed friendly... usually everything has a trade... so what does the rxp do better than a gpr hull

  5. #5
    thewhitewonder86's Avatar
    Join Date
    Aug 2007
    Location
    East Lansing, MI
    Posts
    121
    Quote Originally Posted by breon View Post
    so... if the rxp hull isnt speed friendly... usually everything has a trade... so what does the rxp do better than a gpr hull
    The engine is what keeps the rxp in the game. Like it was said above the srock rxp engine in a gpr hull does about 80 mph, whereas the gpr has to modify the engine to get to that point but in the same token the rxp needs a whole lot of modifications to do 80 because of hull design.

  6. #6
    Quote Originally Posted by breon View Post
    so... if the rxp hull isnt speed friendly... usually everything has a trade... so what does the rxp do better than a gpr hull
    Here's what I think some people need to realize about the GPR hull, and it was brought up by Vern a week or so ago..........it's a fast hull because it's tunable. You can mess with the intake grate, rideplate, sponsons, and trim tabs for a temendous gain in speed. However, you are not seeing the whole story. Like you said there is a tradeoff......handling. The GPR guys running the 800 grate see a 1mph speed increase, but at the cost of hookup and cavatation out of the hole. They also angle the trim tabs and rideplate for more bow lift, but I believe they lose some sharpness in the turns. I know they lose some handling from stepping their sponsons, but again, it's a tradeoff for top end.

    Say the RXP hull had more tuning options...think of where it may be. Or better yet, think of the GPR didn't have the rideplate or trim tabs....where would it be? Certainly not where it is, I can tell you that much for sure.

  7. #7
    Vern's Avatar
    Join Date
    May 2005
    Location
    Grand Haven, MI
    Posts
    3,594
    +1
    128
    The RXP rides two-up much more comfortably than the GPR. If you will often ride with a passenger, the RXP is much more stable. It is a bigger hull, so it is slower than the GPR, but it is still very fast, stable, and there are lots of mods for it. Even riding by myself, I prefer the ergonomics of my RXP over the GPR. Just my two cents worth ...

  8. #8
    Quote Originally Posted by Vern View Post
    Even riding by myself...
    Speaking of which, I am sick of this situation. Michigan boys get together next summer, end of story.

  9. #9
    Vern's Avatar
    Join Date
    May 2005
    Location
    Grand Haven, MI
    Posts
    3,594
    +1
    128
    Yup yup! We need to do that!! I was lazy this summer and never trailered anywhere, just enjoyed my local waters ... but it is sooo nice in Grand Haven ... there are miles of river, many bayous, Spring Lake (big and fun), Lake Michigan ... all accessible from my lift so to speak. I never get bored with my 'home waters' luckily. Now if the dang water level would just stop dropping ... we need a really hard winter.

  10. #10
    Rampage's Avatar
    Join Date
    Sep 2007
    Location
    Holland, Michigan, United States
    Posts
    2,932
    Agreed =) Im in Holland Vern, bit south of you. Lake Macatawa is gettin low, as well, u need to really make sure ur careful where u ride. I love Grand Haven area. Coast Guard festival is awsome My Great Auncle has a place on Spring Lake.

Page 1 of 2 1 2 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. stage ? vs HP#
    By breon in forum 4-Tec Performance
    Replies: 12
    Last Post: 10-07-2007, 04:52 PM
  2. Compression increase vs. HP gain
    By jpa1300 in forum Yamaha PWC Performance (2-stroke)
    Replies: 9
    Last Post: 03-04-2007, 02:44 AM
  3. RXP speeds vs rpm and impeller pitch
    By Vern in forum 4-Tec Performance
    Replies: 21
    Last Post: 02-10-2007, 11:35 PM
  4. Kawasaki General Engine Power (PS vs HP)
    By jscottmsc in forum Kawasaki Tech Tips and Info
    Replies: 2
    Last Post: 09-27-2006, 01:48 PM
  5. Speed vs. Rpm? Ipellers
    By somefun in forum 4-Tec Performance
    Replies: 7
    Last Post: 05-29-2006, 01:04 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •