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Thread: Big Boost

  1. #1
    somefun's Avatar
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    Big Boost

    Hey Guy's does anyone know how much boost the 185 SC's have? And How much the RXP's have?


  2. #2
    snapper455
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    I think it's 5 and 8

  3. #3
    my stock impeller is putting out better than 7psi, not quite 7.5... with poo poo engine...PR...

  4. #4
    EZ Dock of Long Island Shibby1485's Avatar
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    a big determinant of boost pressure is RPMs... stock 185 HP motors from running appx 7600 rpms whereas the 215 motor runs 8100 rpms.... that 500 rpm difference alone is a significant change in boost (aside from the overdrive gears)

    If i understand you since i know your mods and application... i think you ultimately want to know what would the boost difference be at the same RPM point of 185 overdrive gears versus 215 overdrive gears... comparing the boost level of a stock 185 versus a stock 215 is irrelevant because you are already turning over 8000 rpms on your 185 HP motor

    I think if someone is going to actually have the real numbers and facts on the different in boost between the two sets of overdrive gears at the same RPMs, it's probably gonna be Mark Underwood... just seems like something he'd know... if he doesn't, i'm not sure who will

  5. #5
    somefun's Avatar
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    Shib your right. I was thinking of putting the overdrive gears in the motors so I would be the same boost as the 215 and then install the S3's I have. Do you think I should just put the S3's in and don't worrie about the gears? Is the ratio in the 185 the same as the 215's? and then the only differance would have been the rpm's?

  6. #6
    EZ Dock of Long Island Shibby1485's Avatar
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    nope... different gear ratio... 185 motors have 17 teeth on the supercharger gear and 215 motors have 16 teeth on the gear.... and the overdrive gears to mate up to them obviously are different.

    so in order for you to run the RXP overdrive gears you also need to install a new supercharger gear which probably means buying two new sets of clutch kits and two sets of overdrive gears for your boat

    $$$$

  7. #7
    David 1 FAST VE's Avatar
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    Shibby I thought you could just change the gear on the motor?

    http://www.4-tecperformance.com/inde...products_id=59

    Or is this just a GTX thing??

  8. #8
    Site Admin Green Hulk's Avatar
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    Quote Originally Posted by 1 FAST VE View Post
    Shibby I thought you could just change the gear on the motor?

    http://www.4-tecperformance.com/inde...products_id=59

    Or is this just a GTX thing??
    This is all he needs. Its a complete gearset kit

  9. #9
    SHIFT's Avatar
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    Quote Originally Posted by Shibby1485 View Post
    stock 185 HP motors from running appx 7600 rpms whereas the 215 motor runs 8100 rpms....
    mine runs 69mph (112km/h) at 7800..

  10. #10
    EZ Dock of Long Island Shibby1485's Avatar
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    oh man that's awesome!! i didn't realize the rotax racing overdrive gear set came with the gear and needle bearings for the supercharger as well... that's awesome... good looking out david!

    somefun... i looked to see if you could buy the RXP overdrive gear separately from BRP to see if it was cheaper, and from what i'm seeing they don't sell it separately, so if you wanted to go this route Rotax racing is your only option i think... 460 per motor... $920 gets you the gear for the motor and the gear for the supercharger and it would appear new ceramics, but forget those since ur getting metal washers now anyway. something to think about i guess $960 to crank up the boost even a bit more

    you have an extended warranty on that S200?


    SHIFT.... you have an RXP? get the rpms up to 8100 and you'll see more speed
    Last edited by Shibby1485; 12-08-2006 at 04:08 AM.

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