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  1. #1
    fabrication guru rapidacceleration's Avatar
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    switched to open loop cooling on my SC 4-tec XPL

    heres why i decided to get rid of the closed loop cooling.
    when i put the 4-tec in the XPL hull i used a internal heat exchanger that i got from one of the MAZ-DOO guys. it worked great but was real heavy. i would guess like about 25lbs or more when full of coolant. and thats just way to much weight for this already heavier then stock boat.
    well the open loop cooling worked great, the motor managed to stay under 170 after a hard hour or so of ridding, the only prob was the exhaust seamed to get a bit hotter then ussual. the water runs from the head to the exhaust like a older 2 stroke would. so your putting hot engine water to the pipe. i may use the stock half inch line for the exhaust and put the cooler lake water right to it. I had added a 3/4 ID line from the pump for the engine. the smaller nozzle ring got it off the limiter but id still like to trade some of the bottom end (crazy quick off the line) for more on the top. think im going to switch out props next.


  2. #2
    R.I.P. 11's Avatar
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    That is very interesting because I am sure lots of people here are eager to go open loop.

    That will open many new ride plate options.

  3. #3

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    Daniel, I think it's overheating more because the thermostat is staying closed until a certain temp. if it's around 180 degrees, the water dumping into the waterbox will be too hot and when the thermostat is closed, it won't get enough water. egt's start coming on at around 200.
    tap another fitting in the pump for the exhaust.1/2 is more than enough. than install a ball valve on that line. start playing with that valve starting with more water so you don't burn up any couplers. go with as little water as possible before you trip the egt sensor. you'll probably pick up some rpms in the process.once you find the setting with the best performance, install a 80 ohm resistor in series with either wire going to the egt sensor.(I'm assuming the setup works similar like a rxps)

    also if you have access to a gtx pump(10 vein) you should try that in your setup with a stock 155mm 3 blade concord 15/20. if you have a setback d pump in there already, this pump will bolt right up with no mods. what is the rev limiter on your setup. if you can turn that pump around 7700 rpm with a 85mm nozzle, I bet you'll be in the low 70's(and I'm being conservative)
    Mike

  4. #4
    fabrication guru rapidacceleration's Avatar
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    there is no more water pump or thermostat now. the water comes straight from the pump to the bottom of the motor were the waterpump would normally push coolant threw. its exactly like a older 2 stroke setup would be. ive got the factory 1/2" waterline capped off but i think im going to use that one now for the exhaust and add a fitting at the end before the waterbox to pull some of the water out before it all dumps into the waterbox. thinking about welding up the 3 holes so they are half the diameter they are now and useing a water regulator to dump extra water only above a set rpm into the waterbox directly. then im going to add a billit 3/4 bilge fitting for the exiting water coming from the head, basicly two seperate open loop cooling systems, one just for the motor and one for the exhaust. still all just experimental. so any info or sugestions are greatly welcomed and apreciated.
    now im hitting 7700 rpm with a 84mm nozzle on a scat 12 vein with a 16-23 pitch impellor. not sure of the top speed yet, still havn't got to GPS it yet but i can still say it smokes a stock RXP in every way. and the holeshot is crazy quick like nothing ive ever rode before. and im still on a stock 185 motor. once i work out all these other things im going to build a stage 2 RXP motor to switch out with this winter.

  5. #5
    Nonstop, all day, everyday. 01xdime's Avatar
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    HA HA Thats sick! I love it!

  6. #6

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    I was thinking about doing the same thing with my RXP when the wanantee runs out, remove the thermostat and cool the engine with lake water. So someone out here go ahead and try it and let us know.

  7. #7
    Hydrotoys's Avatar
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    Dan,
    I'm going to probably need to talk to you about this pretty quickly.

  8. #8
    fabrication guru rapidacceleration's Avatar
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    cool, i just gotta find some time to cut out a few more blockoffs now.
    i need another one for the 4tec yama-doo SUV also. that projects almost ready for testing too

  9. #9
    Hydrotoys's Avatar
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    I'll need two. Let me know how much and how soon. I'm thinking I'd love to go open loop with the GPRXP.

  10. #10
    Moderator beerdart's Avatar
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    TTT

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