08-16-2006, 09:14 PM #1
Gp1200 old news for some, but still fun...
Took the GP to Egret bay Tuesday, the weather was hot (94 deg.) and windy. But I added some parts and wanted to try them out. Started making full throttle passes, wow the hole shot, med range and top end felt great, but the water was too rough (3 to 5 inches of wind chop) didn’t try to lean it down enough to make the RPMs fall off. It ran 63.8 for about a mile, both ways. So I put the 5 deg. nozzle back on, and the top speed picked up 1.1 mph. That’s 64.9, I was pumped, and it gets there like right now. I know this is not fast by today’s standards, but for stock ports and compression this is not to bad. Took it home and pulled the plugs to check the ports, just to make sure that they were not ported. Fun factor 100%
Fresh top end
Riva FAs No chokes
Protec intake grate, plugged and sealed
Solas XO 13.5 / 18.5 ( Thanks Carl for a great job)
Riva limited ride plate (machined .060 to remove the hook)
Trued and filled hull
63.8 with 0 deg. nozzle
64.9 with 5 deg. nozzle
Last edited by Darthraider; 08-16-2006 at 09:50 PM.
08-16-2006, 09:30 PM #2Originally Posted by Darthraider
As far as holeshot, I know what you mean. When I am low on fuel with the trim one notch up from being all the way down, and leaning my 200lbs a** over the bars, it almost unhooks coming out of the hole.
For reference I am running a Solas J 14/20 repitched by Group K, (the exact pitch I don't know), spinning 6950 in the Texas heat. Last fall I spun 6970-6990 at 66.1 mph. Now in the heat of the summer, after filling the intake grate, ride plate and sponson bolt holes in, and sanding them smooth I am running between 66.2 and 66.9 at 6950. Hopefully this fall, in the same conditions I ran 66.1 in, I will hit 67 or better. My signature will not be updated until this fall.
08-17-2006, 12:06 AM #3
Great numbers Darth!! is the top end stock or overbored? I was also wondering about your compression mine was 125 with new top end bored .5 over and stock head. The numbers are great I never got better than 62.8 on smooth water 1-2" chop with spec pitched XO from impros. I tried a modified XI I got from Carl Payne but had mechanical issues and was unable to get good numbers. Sounds like the sealing is really working on these. I have a slightly damaged XO that is basicly like new I think I will send it to Island for repair and this pitch. I am selling this Ski and I would like to post some good numbers before I do. The ski leaps out of the hole just seems to top out early and the porpoising is a bitch I have shimmed this plate down in the rear and lose speed less porpoise shimmed down in the front more porpoise I cant seem to get the right combo on it.
Rejeted stock carbs with dual feed
3" Power Plenum
R&D ride plate untouched
R&R spacer with Boyesson pro reeds and stuffers
Jetworks valve on stinger
Lever drop nozzle homemade
Umi Steering with Renthal Bars and ODI grips
Sanded hull not sure how true previous owner did it.
Last edited by OsideBill; 08-17-2006 at 08:46 PM.
08-17-2006, 11:28 AM #4
GREAT #'s DARTH, Sure must be a different ride for you from the pissed off paperplate's!!!
O/SBILL.. you are right there...as you shim the GP down on the front of the plate, you will get looser/faster,but the nose will ride higher and then fall off .. thats the downside of this shorter hull ,the happy medium is all we can ask ..a change in your sponsons 'set' may help a little too..let your bender know what you are looking to do,what and when its doing it .. maybe a tweek to the edge on the XO is all you need.
Has anyone tryed to add to the length of the GP hull (not just the plate) with an improvement? Use a set- up like rear-mounted hull trimtabs as used on other makes of skis?
OR a deeper setting grate like ones offered aftermarket on the WR's ?
I know top loading it can do alot ,but it has to run clear water....????
Last edited by w/rpm500; 08-17-2006 at 11:42 AM.
08-17-2006, 07:10 PM #5
97Gpsleeper , You will blow my doors off. The plug is made from 1 inch closed cell foam, from a shop floor mat. Had to put .040 shim under the front two bolts on the Protec intake grate because it was warped. I sealed the intake grate with the impeller out it was easy to reach all areas with the 5200.
OsideBill., Its bored .050, and the compression is on the low side but it’s the same on all three. And it does porpoise on top end, going out in the morning to work on that.
Last edited by Darthraider; 08-17-2006 at 07:23 PM.
08-17-2006, 09:11 PM #6
On the subject of adding Length:
I was at GroupK in April and was talking to Harry about handling of the GP and he explained that in 99 they did away with the trim tabs and that there was some aftermarket ones available but they were not real good. He told me GroupK had made some from aluminum and filled the void left on the back part of the ski to make it flush. he told me it was important to match the radius on the front part where it meets the hull as best I could and make the rear square to the hull he also showed me a stock ride plate on another ski where he had simply welded a rectangular plate in the center area to add about three inches in length kind of looks like the R&D GPR plate less skegs he told me to start long and adjust plate length to the best ride. easy cheap mods. I have yet to try them but felt it was good advice.
I am running Riva sponsons and they are slotted I have them adjusted so the top is flush with the mounting bracket I know you can also tilt the bracket but have not expeimented with this it is also level with the bond line. I will be going out again in two weeks and will be able to make some adjustments and experiment what do you suggest?
08-17-2006, 09:31 PM #7
Darth, do you have any trim tabs? Is your GP a 98, or 99. The early 98's came with the stock plastic junkers that dragged, slowed the ski down about 5mph before they broke off. The later 98's did not have trim tabs because Yamaha just extended the hull to where the trim tabs would have been. Riva & Protec make trim tabs for the later 98's and 99's that are smaller than the 97 and early 98 tabs. If you have a later 98 model I would go ahead a get the trim tabs from Riva or Protec. Being that you are a machinist you may want to make your own.
When are we going riding?
Last edited by 97GPSLEEPER; 08-17-2006 at 09:33 PM.
08-17-2006, 09:37 PM #8
o/sbill.. Since every ski is a different ride... id say put the plate back to where is fastest.. down in front.. then play with the sponsons.. my guess is your looking for speed not handleing... try the sponsons in all positions ,thou IMI the best speed will be with the front set up and the back slightly down as the sponsons set to low is pushing the nose back down at speed... this will be one loose ski so watch yourself..look for the gp bible .. i'll try to find it for you monentarily
Last edited by w/rpm500; 08-17-2006 at 09:49 PM.
08-17-2006, 09:52 PM #9
Hey 97, Lets look for a spot half way, and go.... It's a 99
08-18-2006, 09:30 AM #10
I am a little more than an hour away from Houston. I would like to ride somewhere different. I am an 1 -1/2 hours away from Sam Rayburn, this is the best lake in Texas in my opinion. You could make it to Rayburn in less than 3 hours. A couple of guys from the forum are planning on making a trip to Rayburn in late October, early November. You should try and make it to Rayburn then.
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