Page 1 of 2 12 LastLast
Results 1 to 10 of 11
  1. #1

    Loss of rpms in turn.

    Why does the steering nozzle have ridges built into the sides which make the venturi oval instead of round?
    I'm am asking because I noticed that when the nozzle is turned to the extreme left or right that these ridges effectively block a large part of the water stream.
    Could this be part of the reason why the C180 looses RPMS when turning hard and also why it wont do 360's or is there a valid reason why it is oval?
    Do the skis have these ridges as well?

    I am thinking about portiing things some to smooth out these ridges and make the venturi more round than oval. The metal there is almost half an inch thick so I dont think it would weaken the nozzle.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	nozzle.jpg 
Views:	76 
Size:	1.28 MB 
ID:	72263  

  2. #2
    spd5535's Avatar
    Join Date
    Jun 2007
    It does that in my Utopia as well. It must have to do with physics, but I can make mine do a 360. Be careful with the modification venturi, there's a lot of pressure that is put on those things at WOT. Would hate to see something explode from the force.
    Last edited by spd5535; 05-10-2008 at 09:49 PM.

  3. #3
    Found my answer. Let the porting begin. I will let you guys know the result.
    See attached PDF.
    Attached Files Attached Files

  4. #4
    Jeepster's Avatar
    Join Date
    Jul 2007
    Quebec, Canada
    It's not only that, the first years of the C180 have a les effective entrance of the water intake, so that when you turn them you actually loose some speed. Since i modded mine, it is not reducing speed in turns now, don't know if it's due to the added power, Solas Impeller, or what.

    But thanks for that hint, i'll remove the steering nozzle and will make it smooth allaround, it can not be bad.

  5. #5
    I was just about to get out the die grinder when I found this link.

    This looks like a much better way to go about porting out the ridges as everything is sure to remain perfectly symmetrical.

    Jeepster, with the mods that you have now will your C180 do 360's or have you had a chance to try.

  6. #6
    Jeepster's Avatar
    Join Date
    Jul 2007
    Quebec, Canada
    360's are definitely not a problem with the C180, the hull is just hooking great on them, so you just need to get a hold on how to do it with them, you blast WOT straight, back throttle off at 75%, steer radically, and push back WOT while'll do a 360 easily...! But remember to pull back off the throttle once it spin your engine will spin free the impeller in the pump....not good for your wear i feel the boat unhooking, i pull back the throttle before the pump unloads. Here is a video of it (but it is not my boat).

    And yes the mods have put more punch into the ride so now it is even more easy to do them.
    Last edited by Jeepster; 05-12-2008 at 07:52 PM.

  7. #7

    I used to own a speedster 150 and all you had to do with it was WOT and then quickly turn the steering one way or the other and round she goes. Very fun way of freaking jetboat newbie passengers out.
    Tried everything I could think of to get my C180 to spin out but never had any luck, however I never tried backing off like you suggest and then turning and gunning it. Technique is everything i guess!!!
    If this works I am going to be a really happy camper, and may just end up keeping this boat after all.

    I saw a post a few days ago where you said you may be selling yours and if so you would be selling your power adder goodies seperatley. If that happens I will take the intercooler and injectors off your hands if you like.

  8. #8
    Jeepster's Avatar
    Join Date
    Jul 2007
    Quebec, Canada
    No problems, should these parts go away soon you'll be the first one to know.....and i would have a lot bunch of goodies to sell if anybody is interested...

  9. #9
    I found out the real answer to my original question about why our steering nozzle venturi has ridges on the inside.They are to ease the effort it takes to turn the steering wheel.

    Here is a link to the bombardier patent for the design

    and a quote from the patent.
    A turning-aid nozzle mounted in the region of the outlet of a watercraft's propulsion system comprises a starboard inner surface and a port inner surface protruding radially inwardly from the nozzle in such a manner as to obstruct the flow of water from the watercraft's propulsion system. When turning to port, the starboard inner surface obstructs a portion of the water jet exiting the propulsion system, thereby producing an additional turning moment that aids the nozzle in turning to port. Similarly, when turning to starboard, the port inner surface obstructs a portion of the water jet exiting the propulsion system, thereby producing an additional turning moment that aids the nozzle in turning to starboard.
    "Obstruct the flow of water" doesn't sound too attractive to me but I wonder how hard it would actually be to turn without these ridges. I still haven't ported mine yet but will try this weekend. If it ends up being too hard to turn at least its only a hundred bucks for a new one.
    Last edited by cfnnslsq; 05-13-2008 at 07:27 PM.

  10. #10
    deleted double post OOPS.
    Last edited by cfnnslsq; 05-13-2008 at 07:25 PM. Reason: double post deleted

Page 1 of 2 12 LastLast

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Loss of RPM/cavitation when turning left!?
    By kman in forum Kawasaki PWC Performance (4-stroke)
    Replies: 6
    Last Post: 05-15-2008, 08:45 PM
  2. Loss Of Rpm's
    By bling_bling_420 in forum 4-Tec Performance
    Replies: 10
    Last Post: 08-01-2006, 08:41 AM
  3. Loss of RPMS! Help
    By Chrisrokc in forum Yamaha PWC Performance (2-stroke)
    Replies: 10
    Last Post: 06-06-2006, 06:04 PM
  4. Skat Trak SS wear ring/double bearing pump mod loss of rpms
    By Enufpwr in forum 4-Tec Performance
    Replies: 11
    Last Post: 06-29-2005, 08:11 PM
  5. Jerry - Loss of rpm - loss of speed
    By RXPDAVID in forum 4-Tec Performance
    Replies: 5
    Last Post: 06-13-2005, 03:47 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