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  1. #1

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    Anyone running an 87mm X venturi model on their boat?

    I was going to change from the stock 83mm nozzle to an 87mm nozzle on my Challenger 180 CS. I was thinking this would be ideal for a boat, as it seems more water flow would be more important than the highest water exit velocity in a boat application. I was just curious if anyone had done this, what their results were, and what impeller/SC combo they are running with it.


  2. #2

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    Definitely something I've been wanting to do. I've tried to buy/trade one in the classifieds periodically over the past couple of years, and I never get a bite. Trouble is, we need one off an RXT-X, and most of the "X"s converting down to 83" nozzles, that would have an extra 87" to trade, are the RXP-Xs. Seems it would make it explosive off the line, and I can't see it hurting top speed too terribly much either, like the 3-blade props do.

  3. #3

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    Curious why you say you would need one off a TX? All X models have trim, so the bosses would not be tapped for a non-trim setup if this is what your referring to. I have also considered this, and will be trying it out. Also I was planning to run a 3 blade prop, but I take it from your comment you have done so, and don't recommend doing so?

  4. #4

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    Quote Originally Posted by boostaholic View Post
    Curious why you say you would need one off a TX? All X models have trim, so the bosses would not be tapped for a non-trim setup if this is what your referring to. I have also considered this, and will be trying it out. Also I was planning to run a 3 blade prop, but I take it from your comment you have done so, and don't recommend doing so?
    My thinking that an RXP-X venturi wouldn't fit, only comes from my experience working with the non-"X" models, so there's a chance I could have it wrong. As far as the regular RXP, the venturi will fit our pump, but you won't have a place to connect the steering nozzle... I'm just assuming the difference is the same between the P-X and T-X.

    I've twice tried to run with a three-blade. First one was a 14/19, and then a 15/19 when I had more HP. I just could not feel any new seat-of-the-pants acceleration, but there's no doubt that I lost a good 3mph of my top end. They say it works much better with an aftermarket ECU with higher revs, but I can't imagine it being better than a four blade. Hell, what would five blades to for us?

  5. #5

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    Nah, the 87mm nozzle fits just fine, it's just a cut down (length wise) 83mm RXP nozzle, same casting. I also have an OEM RXP nozzle I removed all the veins from, and smoothed out the inside, and opened it up to about a 84.5mm diameter, may mess with that too. Surely someone has tried a Riva adjustable ring Venturi nozzle on a boat, what were the effects of the larger rings with that? I've already mocked up the 87mm nozzle with a trim ring and test fit it on the boat. I'm just finishing installing the carbon seal (These are the biggest pain the ass of ANYTHING on Seadoo's if you ask me, and I even have the OEM tools..) Then I'll be ready to run, so I haven't taken the boat out yet. I will either have to drill & tap the steering nozzle bosses on the 87mm nozzle for a no VTS ring setup, or considering just using a rod that locks the trim ring in place, or maybe even set it up with trim. Since I'm planning to change out the "weedless intake grate system" for a standard RXPX/RXP (whatever fits) intake grate, I was considering using the VTS motor that is already there for the weedless grate setup, for trim. These boats run an RXP pump shoe, so it's just a matter of drilling out the hole for trim that is already in the shoe for the VTS motor, or possibly (even better in my opinion) just the cable that the weedless grate setup uses.

    Basically, here are my setup ideas for my boat, just looking to try some things out, see what works and what doesn't

    - SC Upgrade (obviously ) Either a B-kit or Riva S3
    - ECU or Injectors or whatever I need for whatever level of SC I go with.
    - 4" air intake
    - I'd like to have trim, not sure how much of an effect it would have, but very curious especially since it would be so easy to install as all parts are already there and wired up.
    - 87mm Exit nozzle (will have to drill out the bosses for a steering nozzle if I don't use a trim ring)
    - Scoop type intake grate (RXP or RXPX, whatever fits)
    - Impeller (I've got a Skat 15/21, Solas 15/22, Skat 160mm 15/20 & Lots of OEM impellers, nothing ideal. And since the 3 blades are already established as not effective, probably end up tweaking an OEM one, or hoping I can turn the 15/22 with the 87mm & B-kit)
    - 2.5" degree pump wedge?? Whats the story with these on boats? Good, or bad?

    Any other ideas?

  6. #6
    mrbtd's Avatar
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    If intersted I have a 87mm nozzle from a T-X $45 shipped is all I want for it. I went with an adjustable set up so no need for it.

  7. #7

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    Quote Originally Posted by mrbtd View Post
    If intersted I have a 87mm nozzle from a T-X $45 shipped is all I want for it. I went with an adjustable set up so no need for it.
    I'm going to take you up on that, if no one else has.

  8. #8
    VX1, Did you get a chance to try out the 87mm nozzle yet?

  9. #9

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    Quote Originally Posted by cfnnslsq View Post
    VX1, Did you get a chance to try out the 87mm nozzle yet?
    No not yet. I got one supposively from an RXT-X, but it turns out to have similiar configuration as the RXP nozzle, that there's no screw holes for the steering nozzle on the top on bottom, so I'll have to tap those myself. Haven't found a tap for an M8 yet.

  10. #10

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    I finally got to try out an 87mm venturi from an X ski, and although the results were unexpected, Im happy to report that Ill be keeping it on. Its one of the best improvements Ive made to the boat.

    My expectation was that it was going to raise my WOT RPMs, so I waited til the summer season here in Florida to put it on, after the hotter lake water had already lowered my RPMs from the winter. I also had to tap the screw holes (5/16 18 NC) to hold the steering nozzle. So, my expectation was that the larger nozzle opening would improve my holeshot, at the expense of a bit of top end push, but that the extra boost from the higher RPMs would end up keeping my top end speed about the same. Basically, I figured the end result would be the same, except better acceleration from a standstill. Since it is also an inch shorter, I thought it could also have a slight negative effect on steering.

    BTW, the stock venturi on a boat is 84mm; it is 83mm for the RXP/T. I have an 83mm from a ski that, in the past, I thought I'd use in the winter to lower RPMs and raise top speed, but it never seemed to have that effect.

    The conditions were clear and calm, 88F degree air, 85F degree water, full tank of gas. First run was made at 2:00pm with the stock 84mm venturi, and the second run was made at 2:45pm with the 87mm.

    Stock 84mm
    WOT RPMs @ 8100
    Boost: 12.1#
    Top speed GPS: 62.7mph

    X ski 87mm
    WOT RPMs @ 8060
    Boost: 11.7#
    Top speed GPS: 64.1mph

    The end result, it inexplicably lowered my RPMs and boost a bit, while giving me about another mile and a half top speed! I should be able to throw on a stock unpitched 15/20, get my RPMs and boost back up, and be at a solid 65mph in the summertime! On top of that, holeshot was stronger, and steering ended up being snappier.

    Your mileage may vary, but this is my result, and Im very happy. I can only surmise that I have increased the engine power so much, but the stock 84mm was choking down that delivery to the water.

    GPS results are great and all, but the best gauge of my new speed is when I get back in the house and me wife says to me with this super-serious look: Youve got to slow down, youre going way too fast out there now!

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