Thread: 85 mph GP
04-05-2007, 12:32 PM #1
85 mph GP
List the reasons why a GP will not run 85 mph
04-05-2007, 12:41 PM #2
1. The hull is too short.
2. In full out modified triple pipe form, most only run 70-75, only a few have went 80 and I think that was spraying.
Last edited by 97GPSLEEPER; 04-05-2007 at 12:44 PM.
04-05-2007, 12:54 PM #3
the gpr's were not pushing big numbers till the pumps were updated .. could the pump/tunnel from the 05/ be modifyed and grafted into the gp??
ARE YOU GETTING 85 ON THE RAIDER??????
04-05-2007, 12:58 PM #4
Hull and pump tunnel design. IMO. I don't even think a 400hp 4TEC motor could get one to break 80.
04-05-2007, 01:02 PM #5
Even if some speed were found in the pump, well tuned triple piped GP's put out 180-185 horsepower and I don't think the hull is going to handle much over that. Most of the GPR's that are running 85+ have well over 200 hp and a much more stable hull. Our hulls are much lighter than the GPR's, common sense would tell us we don't need to make over 200 hp to go that fast, but the weight of the GPR helps it stay in the water going 85+. Our hulls do not lift as well as a GPR hull. Look at some of the pics of GPR hulls when they are going 80+, there is not much in the water. Our shorter hulls will not tolerate as much lift as the GPR hull before porpoising becomes a problem.
04-05-2007, 01:15 PM #6
With that thought on lift ,If one were to affix a wing like tommy has on one of the fountian skis, extend the ride plate and trim tabs, with addition of up dated pump/tunnel.. could this then simulate the gpr hull other than the weight aspect??? just how much longer is the gpr?? I know CARL at ISLAND was pulling big #'s with the XL hull... is this not a longer hull than the gp ,more near the GPR in size .. where do they vary,trying to find a progresion here.
04-05-2007, 01:29 PM #7
The GPR hull is 3.4 inches longer than the GP hull, but the strakes are bigger which helps contribute to the lift. I definetly think your ideas are a step in the right direction. With a longer but steeply angled plate I think the GP will gain some speed.
In two weeks my wife and the baby are going to be gone for 1-2 weeks. During this time period I am doing some serious testing. I am so tired of being stuck at 67.3-67.4, I could thump myself in the balls and be more satisfied!! I am going to make the angled section on one of my R&D plates 2-3 inches longer. I will have my current R&D plate with the Group K mod with me when I test the longer plate. I am going to shim down the front of this plate and see which plate ends up being faster. I would be thrilled to hit 68. I know this thread is not about me trying to break 68, but if the longer angled plate works, it will prove the GP hull is too short and needs more lift.
04-05-2007, 01:49 PM #8
JOHN !!!!!..........be nice ........
04-05-2007, 01:55 PM #9
John has not listed his reasons yet. I know he is pretty crafty modifying hulls. Does he have reasons he thinks a GP can go 85? Where u at John??
04-05-2007, 02:16 PM #10
we also at one time talked of moving the intake back at least the trailing edge.. IMO some makers build ONE grate that fits MULTI skis while others build individule ones(more time spent testing/ proving each ).is there one that will scoop the most??If we're considering a longer plate/tab mod that may have to be experimented with... I talked with BILL at JET DYNAMICS .. He sold me his grate for the WR ,and said he had try'd a plate of his own making that did not show improvement to an existing aftermarket, so he did not produce one . For the WR he recomended a highest tunnel in the plate that would ,I'm assuming,protec, to let the ski rotate back more .. meaning set back more onto the plate at a better angle..this would im thinking enable the scoop to scoop more up even thoug the front may be more exposed to air intake... I do have his water cross plate for the GP 1200 , yet have not tried it as of yet to see an improvement ...
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