10/16 vs 9/15 for mildly modified 750sx. Please help recommend

[roman]

Hi everyone.

Im ordering a new prop to finish off my 750sx upgrades. I would like to know what the recommendation is. This is primarily my girlfriends ski, and she would love it to have some more bite down low to pull out of the water like my 08 SJ does (not possible I know, especially given I have a full bolt on 701). Not sure if it matters, but she is 135lb.

-Stock port 750sx jug (the good numberless one)
-Stock hull
-Lime green head from ss/xi
-750 sxi cdi for better timing
-Factory pipe, the one that has the exhaust outlet in the middle of the expansion chamber.
-Stock waterbox
-SBN44 carb

I will add a 650sx nozzle with the prop upgrade as I understand that is key to down low power.
Does a stubby cone make a big difference?
Currently it is on the stock aluminum prop.

We only ride inland lakes really, jump some boat wakes, run through the ski slalom course, and try to do our own setup wake jumps and some basic tricks like subs, 180 slides, and jumping around. Im not huge on doing topspeed runs on it due to instability, but she somehow has yet to fall off doing WOT runs on it. We dont need more topspeed on it, but im not sure she wants to lose top speed on it when we race other jet skis lol.

Thanks for the advice!

 

[Quinc]

Either one will make a big difference over the stocker. Call up Glen at impros and he will tell you exactly which one you need. Doubt the pump cone will make any noticeable difference.

 

[kevbo]

That pipe with a low port cylinder will work with higher pitch impellers. I have not tried the Hookers so Im not sure how they load. The lowest pitch Solas Dyna fly is probably a little too much load. The 12-18 small hub Concord would be close. Look for no more than 1.5 inches between the blades. Im using the standard concord 11-16 in a 650sx and it turns 6700 RPM at 43mph with good throttle response. This prop would need an sxi cylinder in order to spin over 7000.

 

[Pro-pulsion]

Just thought I would toss in my quick .02 but when I modified my 650sx I put on a Skat-Trak 10/18 as recommended by Impros and it was a huge improvement across the board. I really liked the gains the Skat gave me and wouldn't hesitate to recommend that as an option

 

[john zigler]

Looks like you are in MI? (Elevation will make a difference on impeller recommendations)

I would go 10/16. IMO 9/15 is going to fall flat in the mid range. Especially with a 650 exit nozzle. I would NOT combine a 650 nozzle with a stubby pump cone. The short pump cones allow the water to collapse sooner coming out of the stator section, increasing exit nozzle volume. results are similar to a larger nozzle bore. The 650 nozzle is already pretty big, and I am betting you will loose too much pressure, and cavitate if you have both.

I have Kawasaki Hooker impellers in stock if you need;

https://watcon.com/products/kawasaki-hooker-1

 

[john zigler]

Here is a video I did a while back discussing impellers;

 

[fastgtfairlane]

I think you'll be surprised what the 750 can do especially with the sx cylinder. You have the proper setup power wise. The stock impeller is definitely your setback. +1 on the hooker 10/16. I have a 9/15 in my x2 with same basic setup as you and it's not enough. Any skat big hub swirl in that pitch range will also work well. Change your impeller first, then if it's still not enough, then try the stubby cone or larger nozzle for fine tuning. You may also have to adjust the carb after you change the impeller because you're changing the load of the engine. Also how you have the screws setup on your headpipe can help bottom end. A restrictor going into the stinger or flow control valve will dry the waterbox out at low rpms