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Thread: Loss of RPM

  1. #1
    steved's Avatar
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    Loss of RPM

    Have lost RPM from 8150 to say 7800/7900 re-shimed SC all ok. Have a silicon intake cooler this time water in boost hoses ( not good ) . Has this happed to others and also what was your loss of rpm. been up all night but can only find the Intercooler problem !! other than that all looks ok, even checked prop and liner all OK.

    Thanks
    For any help Steve




    Rotax SC wheel
    Silicon cooler
    42 intectors
    Riva intake pipe and filter
    Riva Skat 15/19 SS wear ring
    81mm Nozzle
    Riva exhaust Mod box


  2. #2
    rior1's Avatar
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    hi steve,iam still down as well 7850 but its better than the 7450 i was turning the other day ,my speeds are back .i think iam still slightley over on the oil but not much at all now just over middle.
    ive been watching other peoples rpms and this seems normal around now maybe it is heat "u wouldnt think it with this weather "

  3. #3
    H2HO's Avatar
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    Mine is down at 7720 and speed at 65.1, it seems to be heat related. I am going to check my impeller pitch and supercharger during my next service to confirm this is actually heat related or not..... water is in the 90's here in Tampa.

    Didnt you guys get a lot of flooding out there in the UK????

  4. #4
    steved's Avatar
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    Plenty of water over here.

    I can only put my loss of rpm down to the water in the intercooler always been a steady 8150 all year ?

    Left out in the open prop good liner good no leaks so not sure ?

    any ideas?

  5. #5
    Yamaha tow boat RIDEALLDAY's Avatar
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    I was running 8120-8140 at MB III and now in Dallas I'm at 7920, 90-95 degrees and fairly high humidity, for Dallas. I've searched my ski over, replaced the wear ring, went back to my stock air intake. It just feels slow, I've been told it's the heat.

  6. #6
    H2HO's Avatar
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    Quote Originally Posted by RIDEALLDAY View Post
    I was running 8120-8140 at MB III and now in Dallas I'm at 7920, 90-95 degrees and fairly high humidity, for Dallas. I've searched my ski over, replaced the wear ring, went back to my stock air intake. It just feels slow, I've been told it's the heat.
    Wow this heat and humidity sure makes a difference. I wonder if there is a place to put an icepack near the hose to intercooler????

  7. #7
    Site Admin Green Hulk's Avatar
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    It's amazing how much the heat and humidity can affect our skis. Thats why i love having the adjustable venturi nozzles. When the temps come up i just pop in a bigger ring to get the R's up.

  8. #8
    Moderator RX951's Avatar
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    Quote Originally Posted by RIDEALLDAY View Post
    I was running 8120-8140 at MB III and now in Dallas I'm at 7920, 90-95 degrees and fairly high humidity, for Dallas. I've searched my ski over, replaced the wear ring, went back to my stock air intake. It just feels slow, I've been told it's the heat.

    I'm still at 7920. Its hot here......

    waiting for more hours on the motor [13 now] and some cooler weather.

    Also gonna install some flow-rites

  9. #9
    southampton u.k boohoo's Avatar
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    Don't think this is a heat problem as steved and rior1 are both in the uk...and it's far from hot at the moment!!..steved try disconecting the hose that goes to the t/b and go ride with the seat off have a look to see if any water comes out under load?.How long has the xs been fitted for? only thr rotax i/c that seems to last the distance
    cheers jon

  10. #10
    steved's Avatar
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    Quote Originally Posted by Green Hulk View Post
    It's amazing how much the heat and humidity can affect our skis. Thats why i love having the adjustable venturi nozzles. When the temps come up i just pop in a bigger ring to get the R's up.
    We do not get any heat in the UK not as you do no this has just happened but it is the RPM moving from 8100/ 7800/7900 that worries me cant find noting wrong .

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