Thread: Bored Nozzle and Thrust question
03-07-2011, 07:41 PM #1
Bored Nozzle and Thrust question
when you open up the exit nozzle to 87mm, what actually happens? I understand it allows more water to get out the rear, hense more push or thrust part,, but what did this mean? was there "leftover" water in the pump,prop,intake , or before "areas" that couldn't be processed and now that "extra" water can be?
If thats true, then all the skis should have it done.
will it scrub or help top end? I'm guessing it would help the holeshot at least if your getting more thrust out the back.
does the steering nozzle need boring too? I heard the ski acts funny if you dont do that one also. is that true?
how does boring the nozzle affect the 5-vane,6-vane-8-vane stators? do you need to change a prop too? since your movng more water thru the pump, i would think so. you would need a different pitch to accomadate the higher volume?
Last edited by bowsniper; 03-09-2011 at 11:56 AM.
03-09-2011, 07:41 PM #2
Boring a nozzle will most definitely decrease top speed. It will, to a point, enhance bottom end.
I swapped the grate on my Jetmate from 90mm (!) down to a 76mm, and gained 2.4mph on top.
There were some posts on making sure your steering nozzle was (I think) 2 mm or more larger than your pump nozzle.
Call Dave at Impros and bounce your questions off of him. I talked with him for half an hour on my Jetmate project.
Side note: I have always disagreed with this need for "Low end grunt" on a PWC. How often do you ride at 1/4 throttle? I watch my tach, and I'm up over 6,000 rpm in less than maybe 2 seconds. Exactly how much help is this low end doing during that time? Unless you're setting up to backflip waves in the surf, and don't have 3 seconds to get up to speed, I think this idea of low end is a misnomer.
03-13-2011, 01:39 PM #3
Boring the nozzle will give you more low end and midrange since you are increasing the VOLUME of water going oout the back of the pump.You will generally lose top end though because with the larger nozzle, you don't have as much VELOCITY now. You can bore the nozzle out to 87mm and install an Adjust-A-Thrust. With this setup you get the low end and midrange of the large nozzle, but the top end of the small nozzle. The steering nozzle needs to be 2-3mm larger than the exit nozzle.
03-14-2011, 08:42 AM #4
Thanks. I'm planning on getting a ATT. I'll let ya know.
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