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Thread: pump tunnel mod

  1. #1

    pump tunnel mod

    just looked in the pump tunnel at the rear of my new sho and found a rubber partition behind the reverse bucket covering the exhaust outlet. have never seen this on any of my other skis [gp1200s etc] is it there for a reason or just to quieten down the exhast. i removed the rubber flap and started it on the trailer and it sounded much louder just dont want to do any damage if it needs to be there. only reason i can see is to quieten down the exhaust or to stop water swishing back into the exhaust when in reverse.


  2. #2
    krenzema's Avatar
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    Quote Originally Posted by pav1200 View Post
    just looked in the pump tunnel at the rear of my new sho and found a rubber partition behind the reverse bucket covering the exhaust outlet. have never seen this on any of my other skis [gp1200s etc] is it there for a reason or just to quieten down the exhast. i removed the rubber flap and started it on the trailer and it sounded much louder just dont want to do any damage if it needs to be there. only reason i can see is to quieten down the exhaust or to stop water swishing back into the exhaust when in reverse.

    Never seen them on a PWC, but thru hull exhaust flaps are normal on powerboats to prevent raw water inversion. Yamaha obviously thinks you need them, so try riva's free flow kit if you want a louder ski.

  3. #3
    It's not the destination, it's the journey!! Rip'nTear SHO's Avatar
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    when i had the stock exhaust on my ski....i took the flaps off to make it sound a little more agressive.........

    now that i have the free-flow exhaust on ....i put the flaps back on to muffle the resonance of that 1.8L...which can get very loud, esp at 3-5k rpm.....trust me when i say that exhaust back inversion is not an issue on this ski...its there to muffle sound...

    It does make cleaning the ski a little more difficult...u have to physically pull the flap back to get the hose in there and the silicone spray....does provide some relief to the ears tho....

  4. #4
    BarBayBULL BAR BAY H.O.'s Avatar
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    Yep
    They are called curtains. And they are there for sound suppression. I have taken mine off and done more than 150 hours since with alot of rough water distance runs and not an issue.
    Makes it growl.
    Also makes for easier cleaning back there.

  5. #5
    Ramming speed Mr Zulu! TeamYamSHO's Avatar
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    Okay i have a question..

    I have mine removed on the right side there as if you were looking right inside the pump tunnel. I have the right side removed there by the exhaust.

    Is it okay to remove the left side also?? And if yess how ? I see the reverse lever to the bucket is there, how do i remove that side without damaging it just incase i want to put it back on?

    Do you have both flaps removed??

    I dont wana mess anything up.
    I love a loud ski!
    Im also buying a thru hull when they release one that plus the mods in my sig and a BOV and ill be done

  6. #6
    BarBayBULL BAR BAY H.O.'s Avatar
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    Yes remove both curtains. It is easy.
    Keep curtains and bolts laying around so if you ever want to put back on they are there.
    Not sure on the SHO but on the HO you just gotta peel back the spring loaded arm and it comes off then do bolts and thats it.
    Very Easy.

  7. #7
    Ramming speed Mr Zulu! TeamYamSHO's Avatar
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    I did it

    Thanks mang
    Going to start her later to hear any differences

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