05-10-2007, 02:27 PM #1
HELP! I am stuck at 75.5 mph !!! GROUP K MOTOR
Ok I have been working on getting this ski running 78mph to 79 to compete with two freinds of mine that run Jacked UP RXP's.
I have been on the phone with all the gurus and THEY ALL HAVE been VERY helpful. But I am missing something so I will post what I know I have, And maybe the speed demon can be found so I can KILL IT! .
2002 1200 motor now 1390 group k motor.
hull has 120 hrs on it
OLD style r&d ride plate modded by me to for top end.
new wear ring SS
plugs indexed and j gapped
Jet works mod with 3/8 hose
concord 14/20 pitched to 14.5/24
# 3 cylinder dumping water over.
pilot 95 mains 120
1 turn out on lows
1.5 turns out on highs # 1&2 cly #3 at 1 7/8 (plug looked lean.)
(I have 115 pilots and 125 mains on the way)
pump is sealed and shoe is not hanging.
1200 R&D intake
2002 tabs (metal) shimmed .034 front two bolts .054 rear bolts
I have not filled any holes in shoe or ride plate or tabs. I am not sure I am where I want to be yet.
Here is the storie:
lately I thought maybe the impeller I pitched might have been out of wack? 75.5 mph @ 7210 rpms
So a freind lent me a impeller that he had done by a pro. it is a 14/20
pitched up to 14.5/21. I tried it this morning. ran 7310 rpms @ 75.3 mph
Can any one help this. I can send pics of any size or flavor. I need 3 mph.
05-10-2007, 02:31 PM #2
05-10-2007, 02:35 PM #3
I think your prop is wack too.
you went from a 14.5/24 to a 14.5/21 and gained 100 rpms, but lost only .2 MPH.
I think you might need to try someone elses big prop.
also you are running a 1200 grate.
why are your tabs shimmed like that? is your ski bouncing without shimms?
do you have the 2 inch spacer installed?
just a few things I can think of
05-10-2007, 02:39 PM #4
05-10-2007, 02:39 PM #5
05-10-2007, 02:40 PM #6
I would start with new style pump and Dynafly
05-10-2007, 02:41 PM #7
05-10-2007, 02:54 PM #8
05-10-2007, 03:51 PM #9
Great lakes call me if you like I can give you my old set up on my group k doing over 81 239-340-1372
05-10-2007, 05:02 PM #10
If Forrest offered you better take it and call him.
The jetting looks way off to me. I run 125m in my unported 1200, I would thing 140 or at least 135 to start off with. Did you talk to Harry at Group-K about jetting? You would also benefit from the new style pump. The shoe could be a culprit as well, what are the measurements stepping up from the hull. Also what kind of angle do you have on your modified plate?
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