Page 1 of 3 1 2 3 LastLast
Results 1 to 10 of 30
  1. #1

    best intake grate for porpoising on GP1300R

    Trying to reduce porpoising on a 2005 GP1300R. All stock now except angled the sponsons. Would an aftermarket intake grate help ? I heard the stock one ( which I have now ) is a POS. Is this a difficult job ? Looks like a bolt on or is it more complex ?


  2. #2
    Hydrotoys's Avatar
    Join Date
    Jul 2005
    Location
    Mesa, AZ
    Posts
    16,712
    +1
    85
    Not really.

    Drop your trim tabs down with two washers on each bolt. This will plant it nicely.

    Also, check your trim position on your handlebars versus the actual angle at the back of the ski. If you have it in neutral, your steering trim nozzle should match the angle of the rigid nozzle.

  3. #3
    Quote Originally Posted by strokersquid View Post
    Trying to reduce porpoising on a 2005 GP1300R. All stock now except angled the sponsons. Would an aftermarket intake grate help ? I heard the stock one ( which I have now ) is a POS. Is this a difficult job ? Looks like a bolt on or is it more complex ?
    The stock grate is not a POS, there are thousands of stock skis running who are not on these forums. BUT most change the grate when they mod for more speed to be safe and for better hook up. You have plastic OEM trim tabs and will require that you shim with a full surface shim to keep the tabs from flexing, otherwise find a set of older (2002) OEM metal GPR trims tabs...
    Aftermarket extended Tabs will help with some aftermarket Plates and the OEM plate to a degree. Bow down attitude reduces porpoising.
    Your best bet is to read read and search for all the info on the net., don`t just start throwing parts at it until you understand what each component provides and why... There are proven recipes for the GPR but as always dial in your ski for the waters and the way you ride...good luck...

    NOTE* I prefer the Worx grate, but hey that`s just me...

  4. #4
    Just relax and enjoy the ride. XLT Chad's Avatar
    Join Date
    Jan 2011
    Posts
    1,284
    +1
    116
    +1
    If you want to see the right way to build a GPR, follow Pale Rider's build thread. The link is down in his signature block.

  5. #5
    I did stagger the sponsons, and put 3 washers on the back of the ride plate ( since this was easy ). If this does not work, then I will put washers on the trim tabs too. Thanks all. I asked about the intake because I saw an R&D intake grate on ebay, but no reason to put something on if others have had bad luck with it.

  6. #6
    Hydrotoys's Avatar
    Join Date
    Jul 2005
    Location
    Mesa, AZ
    Posts
    16,712
    +1
    85
    You put washers under a stock rideplate?

    It sounds like your whole setup is fighting itself.

    Just do this one simple experiment:
    -Set your stock rideplate flat, no washers.
    -2 washers under the trim tabs.
    -Center your trim, to verify that it is neither pointing up nor down.
    -Crawl under your ski, and verify that your shoe is not hanging down, nor any other component is screwed up.

    This should give you a very tight-running gpr with very little bounce at neutral trim.

  7. #7
    Quote Originally Posted by Hydrotoys View Post
    You put washers under a stock rideplate?

    It sounds like your whole setup is fighting itself.

    Just do this one simple experiment:
    -Set your stock rideplate flat, no washers.
    -2 washers under the trim tabs.
    -Center your trim, to verify that it is neither pointing up nor down.
    -Crawl under your ski, and verify that your shoe is not hanging down, nor any other component is screwed up.

    This should give you a very tight-running gpr with very little bounce at neutral trim.
    Mark, he has the plastic OEM tabs, and he is riding 2 up which changes everything. he also needs to know to use a good SS washers that measure the same, not some regular irregular washers...
    +1 stock ride plate flat...

  8. #8

    Join Date
    Jan 2006
    Location
    Texas City, Texas
    Posts
    1,249
    +1
    15
    Quote Originally Posted by Pale Rider View Post
    Mark, he has the plastic OEM tabs, and he is riding 2 up which changes everything. he also needs to know to use a good SS washers that measure the same, not some regular irregular washers...
    +1 stock ride plate flat...
    The point is that a couple of washers on your rideplate and a 100's shim on your tabs is going to make a huge difference on how your craft behaves. No one can give you an absolute formula that will make your boat do the right thing in all occasions. This depends on how you ride, the water conditions you ride in and how much weight is on the boat. You will have to "fine tune" for optimal conditions yourself. Just know that as little as a 10 thousandts washer can make a noticeable change on how your craft rides.

  9. #9
    yes, indeed i have plastic trim tabs so i didn't space those. i read here on an older thread to space the rear of the ride plate to force the nose down. is that incorrect ?.with my son on the back and less than half a tank it would porpoise at anything over 30mph, even with the trim set for the nose all the way down. Only on the most glassy water would it not porpoise.i could reach 74mph on the dreamonmeter without any instability on glass but there was very little of it in the delta on Sunday. nothing hanging down underneath.

  10. #10

    Join Date
    Jan 2006
    Location
    Texas City, Texas
    Posts
    1,249
    +1
    15
    Quote Originally Posted by strokersquid View Post
    yes, indeed i have plastic trim tabs so i didn't space those. i read here on an older thread to space the rear of the ride plate to force the nose down. is that incorrect ?..
    It is correct. Doesn't extra gas (weight) force the nose of your craft down? Shiming your plate causes the hydrodynamics of your hull to change, and this changes casues the nose to go down... at the expense of speed. In your case, you probably would not notice the speed loss, just the stability increase, and as a result of the stability increase a desire to go faster.

    You have to remember that certain mods on these super fast boats will do nothing for them on the top end other than slow them down (ex. spaceing the ride plate) whereas other mods do not have an impact on them at all, since the part of the hull that they work on are actually completely out of the water at higher speeds (ex shiming the trim tabs). Another way of putting it is that the faster a craft goes, the smaller the working part of the hull, (that is the part of the hull that is still in contact with the water) becomes.

    In your case, we are talking about a slower craft operating at a speed range where most of us mortals ride, and this is why some of this info is confuseing. On your boat (30 to 60 mph), both methods will help, and IMHO I would say that shiming the trim tabs (about 100 thousandts) is more efficient at helping to eliminate porpoising whereas spaceing the ride plate (30 to 90 thousandts or 2 to 3 washers) is certainly easier to do.

Page 1 of 3 1 2 3 LastLast

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Best Intake Grate for Hole Shot on RXPX
    By Rxpx-Milf in forum 4-Tec Performance
    Replies: 17
    Last Post: 10-29-2009, 03:26 PM
  2. best intake grate for 1200 xlt
    By pres319 in forum Yamaha PWC Performance (2-stroke)
    Replies: 15
    Last Post: 07-20-2009, 12:54 PM
  3. which is the best intake grate for rxp
    By tottii in forum 4-Tec Performance
    Replies: 2
    Last Post: 03-02-2009, 01:27 PM
  4. best intake grate for a 701 venture??
    By lextoy in forum Yamaha Old School Skis
    Replies: 0
    Last Post: 10-27-2008, 10:58 PM
  5. Best intake grate for xlt1200
    By dongee in forum Yamaha PWC Performance (2-stroke)
    Replies: 29
    Last Post: 07-11-2007, 06:02 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
  •