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  1. #1

    Join Date
    Jun 2011
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    asheville, nc
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    25

    Unhappy Gpr Bad prop spin And slow top speed!!!!!!

    So First off like i said i have got some bad prop spin from idle to about 10 mph. I'm thinking time for a new Prop?? which one should i use? Dyna fly 14/20? spinning 7450 rpm on top with a 13/19 and i'm only like 1 or 2 mph faster then my cousins bone stock 07 gpr! why????????? need some help from the masters of the gpr's. O and it's a 2001 hull with 06 internals...engine, pump, etc... 87mm exit nozzle.


  2. #2
    usually if the pitch is to small you will have prop spin if you hammer it off idle for the first few feet and mph.
    since you didn`t mention is Cav`s badly until you really start moving
    otherwise it is checking out all the normal stuff...

    now, are you also running the HO pump? if you are the concord series prop (small hub) is incorrect for your app...
    by the looks of those compression numbers you should be able to spin up a 14\20, but we are just guessing without more info...
    7450 is hard on the limiter... and those first 2 numbers on the controller look light to me... have you checked the piston wash lately?

    top speed, you really need to GPS, and what tach are you using?

  3. #3

    Join Date
    Jun 2011
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    asheville, nc
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    25
    I'm not sure about the pump. I bought it with the stuff already on it. Been working on dialing it in for the past few months and learned almost everything on this forum!! ( thanks to all btw!!!) How can i tell if it's the HO pump??

    As for cav. It does it some on take off and after a sharp 180. At least i think it's cav. or maybe just prop spin?!! Feels like a burn out...all power and no grip. Does it really bad with two people on it!!!

    What more info do u need??

    Haven't checked the wash yet. 3416 or 4516 seem to work the same for me, should i go up for safey sake?

    My tach is a tiny tach com. I have a gps just forgot it when i went down last weekend!!

  4. #4
    Quote Originally Posted by Monster Machine View Post
    I'm not sure about the pump. I bought it with the stuff already on it. Been working on dialing it in for the past few months and learned almost everything on this forum!! ( thanks to all btw!!!) How can i tell if it's the HO pump??

    As for cav. It does it some on take off and after a sharp 180. At least i think it's cav. or maybe just prop spin?!! Feels like a burn out...all power and no grip. Does it really bad with two people on it!!!

    What more info do u need??

    Haven't checked the wash yet. 3416 or 4516 seem to work the same for me, should i go up for safey sake?

    My tach is a tiny tach com. I have a gps just forgot it when i went down last weekend!!
    bigger engine, more torque and power, so maybe just the pump/prop is not set up correctly...
    take a few pics, look inside the steering nozzle and describe the cone? also take a pic of that...

    since you have raised compression an a FF, I haven`t seen to many people running less than 5516, or 5616 for starters... a lean engine will run real crisp until it`s to late...
    and if that prop isn`t right you may not be loading the engine enough down low to feel the need for more fuel...
    I would def start with finding out exactly what prop and pump you have... can you see any numbers or name on the hub of the prop?
    assuming you have the early pump, you could def benefit with a 14\20 trued, HO pump and the 85mm exit nozzle... unless your area is so hot that you need the rpms, but according to your rpm reports apparently not...

    if your hull is set up correctly, assuming it is set up for speed, and your engine is dialed in, you should be crushing that stock ski off the line and pulling away by a few ski lengths, and maybe 4-6 more mph on top...

    the GPR was never really a 2 person ski, it handle horribly and doesnt like the added weight on the tail... so it is real finicky and will spin a tight prop more than if with one person on it...

    maybe WFO, or Jim and other members can jump in here and explain a little better what needs to be done...

  5. #5

    Join Date
    Jun 2011
    Location
    asheville, nc
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    25
    Ok here are the pix. what do ya think?? The prop says solas concord yf-cd-13/19. the inside hub of the pump is 60mm and the outer is around 160mm. And also i want to set this ski up for wave jumping in a lake. top speed is important but back breaking accel. is what i'm looking for!!
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  6. #6
    Quote Originally Posted by Monster Machine View Post
    Ok here are the pix. what do ya think?? The prop says solas concord yf-cd-13/19. the inside hub of the pump is 60mm and the outer is around 160mm. And also i want to set this ski up for wave jumping in a lake. top speed is important but back breaking accel. is what i'm looking for!!
    That is a small hub pump, most likely original equipment. you need to verify tho that you have the 2" spacer (between wear ring and transom plate) and the correct length drive shaft to use with an HO pump...
    Now that you said you want better bottom end acceleration you would most likely stay with a 13\19 pitch but the larger hub 155/75/22 Skat for bottom end and great hook up in the rough, or a depitched solas YG-DF 14\20... if you go that route (solas) you could always pitch back up to a true 14\20 to gain back some speed if you need more yet. I would also recommend going with an 85mm OEM exit nozzle, HO pump, and a SHO steering nozzle to complete the set up., then you would be equal to or exceed your cousins ski.

    you have to verify what you have. Im am not familiar with the older ski`s and what came with as far as drive shaft length/spacer...
    it sounds complicated, but when this ski gets set up correctly the difference will be night and day...
    right now your not apples to apples with your cousins ski, if that is your goal as far as performance...

    looking at that pick of the wear ring, it looks like a rub spot in the 7:00 position? did you measure for impeller clearance before disassembly? if not stick the pump back in there and measure the clearance with a "feeler" gauge between the prop edges and the wear ring... and that will give you an indication on if that prop had to much clearance at least...

    you could always hang onto that 87mm nozzle that you have if you need to fine tune your rpms for your riding area or holeshot gains...

    if all that gets to costly there are alot of 1300`s running very well with that pump set up and the correct impeller, there might be one in the classifieds now for your app...



    you just need to figure out what ya want to do, read up of all the very good set ups on here and make a choice...

    Theres a bunch of members here who are masters at this kind of stuff...

  7. #7
    1200 stx-r's Avatar
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    Acceleration ?? I can honestly say a reed set up with spacer and freakin port that baby! It woke my ski right the french up! And then who cares what your cousin and his ski are doing because they will be doing it behind you!!! Just sayin ! Pale rider is right about that 7:00 spot u got a tweak in that impeller or some type of mis-alignment. And as far as yamaha making the gpr a 2 person ski----- it's because 1 person skis are called stand-ups and that's not appealing to the some peeps that want to sit and win.

  8. #8
    Quote Originally Posted by 1200 stx-r View Post
    Acceleration ?? I can honestly say a reed set up with spacer and freakin port that baby! It woke my ski right the french up! And then who cares what your cousin and his ski are doing because they will be doing it behind you!!! Just sayin ! Pale rider is right about that 7:00 spot u got a tweak in that impeller or some type of mis-alignment. And as far as yamaha making the gpr a 2 person ski----- it's because 1 person skis are called stand-ups and that's not appealing to the some peeps that want to sit and win.

  9. #9
    1200 stx-r's Avatar
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    Quote Originally Posted by Pale Rider View Post
    Only had my GPR for a short time , but glad you approve of my response!!!!

  10. #10
    PolarisNut's Avatar
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    Had a whole response typed up and accidentally clicked off this screen and lost it.

    Anyway, you need to start with a Concord 14/20 impeller, if you're going to stay with the old pump setup. Sell that 13/19, because it'll never be as fast as an off the shelf 14/20. It was meant for lower power motors.

    The Dynafly is for the 05+ pump, but some do use it on the older ones. I can't comment on that, because I've never tried it. Honestly, if you're looking to do some mods to the boat, I'd just setup an 05+ pump and go from there (it'll cost about $500 with used parts, including impeller). Better hookup, better acceleration, and better top speed. Its a win win, except for your wallet. I gained 3mph by switching to it with a Dynafly on my triple pipe boat. You can use whatever drive shaft you have (yours should be the longer 30" shaft)

    You also don't have the 2" extension. That's ok because it's not a huge gain. Nice to have, but you have to pull the engine forward to install a new mid shaft, to run that extension on the 00-01' boats. I'd only do that if you have the engine out.

    Also, you need to run a 1200 R&D intake grate to hole shot very well. The stock grate is dangerous anyway, so ditch it. The 800 grate is faster, but doesn't hole shot as well. I run the 800, because at my speed level, its faster by almost 2mph, and I just live with the fact that I can't hammer it out of the hole.

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