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  1. #1
    Tampa Bay SAR marine unit
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    what would happen if

    i removed one of the water boxes on my 155hp GTX LTD?

    any noticable gains?


  2. #2
    flyin' the friendly skies airbornexp's Avatar
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    what year is it? id imagine if you removed one you would probably lose a bit of speed due to reduced back pressure and gain more sound.

  3. #3
    Tampa Bay SAR marine unit
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    Quote Originally Posted by airbornexp View Post
    what year is it? id imagine if you removed one you would probably lose a bit of speed due to reduced back pressure and gain more sound.
    02

  4. #4
    Tampa Bay SAR marine unit
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    so id increase noise and loose speed?

    any one else care to comment?


    ski is an 02 GTX LTD 4TEC

  5. #5
    King_Of_Fun's Avatar
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    The '02s and '03s had that complicated double water box system. Be happy with what you have. 58-60 mph is about it. A couple mods and you pick up maybe 2 mph, but you will never be able to run with RXTs and RXPs. But at least you don't have to worry about dropping an SC washer... Ron

  6. #6
    lextoy's Avatar
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    in the 155 htere is no SC. so dropping backpressure in teh exhaust will probably decrease performance.
    in the 185 skis, losing the extra water box only helps by reducing clutter, but no loss of perf. cuz in a SC ski backpressure isnt really important

  7. #7
    Tampa Bay SAR marine unit
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    ok i know im new to watercraft but in automotive apps, a slight decrease in back pressure will increase performance, allowing the engine to breath better, to much and then you lose performance

    and i dont see how backpressure would effect a supercharger in any application, its run off the engine internals, not the exhaust like the turbo setup

  8. #8
    lextoy's Avatar
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    backpressure can only bottle up a Sc ski, however the stock systems are not that restricitive, so opening them up doesnt yeild any gains, until you are into major high performance stuff.
    in PWC a normally aspirated engine usually has a tuned exhaust chamber for optimum performance, start messing with that tuned exhaust and you can destroy performance.
    however in the 4tecs i dont think the exhaust is all that tuned on the 155 skis, but again decreasing backpressure wont yeild anything significant, maybe maybe maybe 50rpm tops.
    probably only in conjunction with an air intake mod, to get more and cooler outside air into the engine.

  9. #9
    Tampa Bay SAR marine unit
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    well i found out what happens lol

    i removed the right water box


    then from all 3 rubber hoses and some 2.5" exhaust tube i had laying around (cleaned and painted to prevent/slow corrosion) i put together a new hose to run from the first water box, to the thru-hull





    also this mod gave it a nice drone at idle and light throttle, 3krpms sounds amazing

    from dead stop, you fully squeeze the throttle, there is no lag time between idle and 7500rpm, the whole ski jumps up on plane almost instantly (or so it feels), didn't gain any MPH still topping out around 56ish (GPS'd), but accel is noticibly enhanced

  10. #10

    Wink

    I know this might open up a can of worms, but backpressure is never, and I do mean NEVER a good thing.

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