Thread: Performance help
06-09-2008, 11:48 PM #1
Hey everyone, so I got my RXP on the water today and was doing some speed runs. I am trying to figure out why my ski is slow. It is a Stage 3 with a Rude. Running a 15/19 prop along with 81mm nozzle ring. Air temp was 85 and water temp was 78. The best speed I could get was 75Mph. This was at 8300 RPM's. My rpms are down a bit from the triple bearing mod and warmer air/water.
I was wondering if anyone has any idea's what could be causing my performance problems? I was testing in mild chop with a few spots where it was smooth.
I figure I should be hitting at least 78 with my setup. Any help would be appreciated!
06-10-2008, 12:04 AM #2
Have you looked at everything on the hull ? Did you match up your rideplate and intake grate ? Do you have OPAS blockoffs ?
Also do you have a 15/20 or a 15/22 impeller you can try out ?
Wear ring, do you have a stainless or OEM ?
06-10-2008, 12:07 AM #3
I was having the same problem.. From what ive been told,
chop + heat + salt = BIG loss...
you will see 3-4 mile difference in summer months.... just try and tune your ski to get the most rpms....
06-10-2008, 12:11 AM #4
PBJ, that could all have some effect for sure. But he should run at least 80+ if he is using the Riva Stg. III +Rude charger. That is somewhat the same setup that I am running except I use a 4 blade impeller.
Last edited by DaveC; 06-10-2008 at 12:21 AM.
06-10-2008, 12:21 AM #5
i have all those mods too..
+ 8800 ecu
Im barely there....
heat is real hard on speed...
from what i hear, everyone coming to mudbug from north, looses alot...
and they spend all night trying to get the results from home with no luck....
Heat and speed are like isrealies and palestinians, they dont get along...
06-10-2008, 09:17 AM #6
I experienced the same thing this past weekend. My rpms were down from 8500 to 8250 and my highest speeds were 76-77mph. The water was high 60's and air was high 80's
06-10-2008, 09:40 AM #7
Hey guys, thanks for all the info.
Dave, I do have RE blockoff's. I have Jim's modded plate with skegs. And my grate/plate are perfectly mated. I have some silicon between the 2 and smoothed it very well so as to make sure there were no gaps that could hurt speed. I do have a 15/22 that I am planning on testing out. Also I do have a SS wear ring. My pump has the triple bearing mod and has been built by Glen at Skat-Trak.
The speed numbers everyone gets... is that with just perfectly smooth glass? I dont have access to that kind of water. There is always a slight chop wherever I go.
There is only 1 place I know that has perfectly smooth water and thats the colorado river. And thats only in the early AM. The problem with that is the temps are over 100 there lol. So I would probally go slower. Its quite amazing how big of a diffrence heat has on these motors.
If anyone knows of a good place to go speed tests in Cali let me know. Maybe I could just plan a trip and do my tuning there.
Thank you everyone for all your input and assistance, I really appreciate it guys!
06-10-2008, 01:32 PM #8
Something is not rite. Your ski should be running 80ish all day long. I am running a x charger with stock ecu and a 15/19 3 blade and run 75 to 75.5 consistantly with 90+degree air and 85 degree water.
06-10-2008, 01:40 PM #9
yeah but is that in smooth glass like water or choppy water?
06-10-2008, 02:59 PM #10
Flat to light chop. I think a light chop actually can help your top speed because it has less drag on the hull. Your idea and my idea of light chop may be 2 different things.
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