Thread: GP 1200 porpoising..
04-03-2010, 09:02 PM #1
- Join Date
- Jul 2009
GP 1200 porpoising..
I own a 98 GP 1200 with the well known porpoising problem. I read forum after, thread after thread to figure out how i could alleviate the porpoising. So i shimmed my stock ride plate in every which way and that didn't work except for a loss of top speed. So i bought a stinger ride plate and that didn't really help at all, even when i tried different shim settings... So is there anyone out there that has successfully tamed their porpoising problem with this machine? And if so what modifications are required? I love my wave runner but it beats the crap out of me on long rides up the river..
04-03-2010, 09:16 PM #2
stock 97 ride plate it's longer then the 98-99 plates. Or a shredmaster too from what I have heard but never been able to compare..
Great ski's though
04-03-2010, 09:17 PM #3
What sort of intake grate do you have ? A toplading grate will pull the hull down and help with hookup. Next question what sponsons do you have ? If stock ,make sure they are all the way down you wont loose speed and it will help with the porpoising. If you have after market sponsons try adjusting them down . Last thing ,are the trim tabs original plastic ones or have they been replaced ? This is very important as plastic tabs cause havoc with the GP1200 hull.
04-03-2010, 09:36 PM #4
Found this on Group K's website.
ABOUT GP 1200 SPEED AND HANDLING - There has been considerable controversy about the wide variation of peak speeds among stock GP 1200's. During our testing we experienced large variations in speed that were caused by stock trim tabs that did not properly fit or seal to the hull. Our tests showed that the stock tabs can account for a loss up to 4 - 5 mph for any GP. Based on these tests, we strongly recommend that the stock plastic trim tabs, on every GP 1200, be replaced with solid aluminum tabs. In particular, we consider these aluminum trim tabs to be mandatory for GP 1200's that are being modified for more horsepower. We have had good results with the aluminum trim tabs (and optional mount kit) from Riva.
Found this here on Greenhulk
Looks like Riva tabs are what you need or you can make your own.
04-03-2010, 10:40 PM #5
- Join Date
- Jul 2009
I am the second owner and from what i can see everything is stock on my GP except the shredmaster ride plate which is a few inches longer than the stocker. So you guys think new trim tabs are the key? Where is the best place to purchase them and are they difficult to install?
04-03-2010, 11:11 PM #6
- Join Date
- Jul 2009
I also have another question about trim tabs. I've read that an early 98 GP had plastic trim tabs on it stock and that later model 98 GP's do not have trim tabs at all just an extended section of hull. I am fairly sure i have a later model because i don't see anything that remotely looks like trim tabs on the rear hull. So, can i actually put trim tabs on my GP if it is the later model? If so where can i find them?
04-04-2010, 09:23 AM #7
I forgot to mention in my PM that I do run with the sponsons all the way down as adam said. I have the factory sponsons. I also have a R&D intake grate.
Here is a link to the trim tabs that I have:
04-04-2010, 11:11 AM #8
04-04-2010, 01:23 PM #9
Have you used or know anyone who has used them..?? (the 98-99 Riva versions)
I have a set, still in the wrapping i got a good while back from Simon (mongoose)
I would use them on my late 98 GP if they could provide a definite improvement in the handling or speed departments..??
The reason I've not went ahead and just fitted them is I've spent hours (way too many) truing my hull..
Then factor in the paint job, which I'm not keen on drilling holes into..
But if they work..!!
Where's my drill..??
Think I'll see where i get to with props and plate angles then fill some bolt holes..
Before i do anything..
For the now the porpoising isn't that bad at all... (there is still some)
Could be making enough power to overcome it somewhat..??
04-04-2010, 09:15 PM #10
The only way the tabs will add speed is if you have an uncontrollable porpoising problem. If the ski does not have a porpoising issue, adding the tabs will slow you down.
I have never installed the tabs on a late 98 or 99. I am sure they work, but I don't think they are the only cure. I can superman my ski with the trim all the way up, on the fuel buzzer, and it never settles into a steady porpoise that causes the pump to come unhooked.
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