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  1. #1

    300x rpm question

    I have an 11' 300x which have the following mods:

    SCOM
    R&D Intake Grate
    Solas 14/21
    Deep Fuel Pickup
    R&D Block off plate

    The question I have is using an iphone app the top speed I'm seeing is 69.4mph and my rpms are around 7440-7460 and I'm thinking that is a lot low. Do you guys have any ideas on things I should check? I know the prop will bring my rpms down but I don't think they should be that low. After waiting for the R&D ride plate I just got it in the other day, I haven't installed it yet but even with the ride plate/shoe kit installed I think my RPMs should be higher.

    Another unrelated question, I ride in lake Erie and a local river. I have never beached the ski and I have hit bottom maybe once but when we were doing the prop install the inside of my pump housing was destroyed. Has anyone else seen this issue? It looks like it was just sand blasted to the point of where the hosing twist it was sandblasted down to nothing. I have replaced it with all new housing, prop, shaft, bearings, whatever else was in there just to be safe.

    Thanks for any help guys!


  2. #2
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    Quote Originally Posted by classic079 View Post
    I have an 11' 300x which have the following mods:

    SCOM
    R&D Intake Grate
    Solas 14/21
    Deep Fuel Pickup
    R&D Block off plate

    The question I have is using an iphone app the top speed I'm seeing is 69.4mph and my rpms are around 7440-7460 and I'm thinking that is a lot low. Do you guys have any ideas on things I should check? I know the prop will bring my rpms down but I don't think they should be that low. After waiting for the R&D ride plate I just got it in the other day, I haven't installed it yet but even with the ride plate/shoe kit installed I think my RPMs should be higher.

    Another unrelated question, I ride in lake Erie and a local river. I have never beached the ski and I have hit bottom maybe once but when we were doing the prop install the inside of my pump housing was destroyed. Has anyone else seen this issue? It looks like it was just sand blasted to the point of where the hosing twist it was sandblasted down to nothing. I have replaced it with all new housing, prop, shaft, bearings, whatever else was in there just to be safe.

    Thanks for any help guys!
    Buy a real gps to check your speed but I think it's right in the correct range. Your rpm does not make since how are you checking it ? Dont go off the max rpm setting its never correct look at It live Should be in the 77-7800 rpm range

  3. #3
    nicjak's Avatar
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    also guessing you probably need to adjust the BOV up

  4. #4
    Moderator #985 lasportsmn's Avatar
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    Quote Originally Posted by nicjak View Post
    also guessing you probably need to adjust the BOV up
    He has it blocked off.
    I would make sure your hose clamps on the air intake system are all snug. The slightest leak will reduce performance. You are correct, you should be higher RPMs and speed.
    Did this slow down occur right when you did these mods?

  5. #5
    nicjak's Avatar
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    thanks GL missed that one, my other guess is hope the op is not reading the max logged rpms.

  6. #6
    I guess I have never really thought about using a different GPS as I have always used an iphone and last year with just SCOM I was doing 72. I am using a different app now I couldn't tell you if its correct. I do have a garmin etrex so I will try that on my next outing. As far as when I'm reading the RPMs it's not off the max RPMs its while I have watching it and riding the ski. I have checked for leaks and haven't seen any unless the bov after the intercooler is leaking which I guess is possible. I will check this as well.


    Any idea on the destroyed pump? I know that in the pictures there is a chunk missing.. as well as the shaft being mutilated.. I didn't do that I was just told it happened when they had to put it in a vice and since the spines were twisted they wern't able to get it apart.. ok whatever I replaced it all not to worried about what they destroyed.. I'm just wondering if what I'm seeing on my pump is common, I don't really want it to happen again so I'm trying to find out what caused it in the first place. The blades on the stock prop are all fine. I undersand that its a harder metal but I'd expect some marks?


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    Thanks for the input guys!

  7. #7
    nicjak's Avatar
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    wow someone must have been doing some series dredging there i would be a little concerned of how much sand is actually still in the cooling system of the motor. it most definatly isnt common, oh well actually it is too someone that has no idea, not blaming you in any way some people know no better, keep the ski out of the sand and rocks, try anchoring it if you have to beach it rock it about before starting it this will help dislodge some of the sand out of the pump.
    you said you have the bov blocked so that wont be the problem, it is a little bit of a mystery with such low rpms. i suggest you go back out do a WOT run look at the display and take note of the actual rpms and also the boost at those peak rpms, then get back to us

  8. #8
    That's why I am so concerned. I have never once beached it. I always anchor it in like 3ft of water. I guess I will just watch the new pump housing and see if it happens again then worry about it. I will do what you said and get back to you. Thanks!

  9. #9
    ultra300x 702's Avatar
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    Quote Originally Posted by classic079 View Post
    I guess I have never really thought about using a different GPS as I have always used an iphone and last year with just SCOM I was doing 72. I am using a different app now I couldn't tell you if its correct. I do have a garmin etrex so I will try that on my next outing. As far as when I'm reading the RPMs it's not off the max RPMs its while I have watching it and riding the ski. I have checked for leaks and haven't seen any unless the bov after the intercooler is leaking which I guess is possible. I will check this as well.


    Any idea on the destroyed pump? I know that in the pictures there is a chunk missing.. as well as the shaft being mutilated.. I didn't do that I was just told it happened when they had to put it in a vice and since the spines were twisted they wern't able to get it apart.. ok whatever I replaced it all not to worried about what they destroyed.. I'm just wondering if what I'm seeing on my pump is common, I don't really want it to happen again so I'm trying to find out what caused it in the first place. The blades on the stock prop are all fine. I undersand that its a harder metal but I'd expect some marks?


    Click image for larger version. 

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Size:	83.0 KB 
ID:	276259

    Click image for larger version. 

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ID:	276260


    Thanks for the input guys!


    I have a good idea who did your pump. What shop was it ? Your pump looks like some rocks went through it. My pump liner was scarred by some sand but you have missing chunks. After you blocked off the BOV did you cap the air intake box? Your speeds are low with that expact setup om my 2010 300x i was just under 74mph at 7600-7700 rpm. Clearly your rpms are off check your hoses clamps and possibly exhaust filter

  10. #10
    nicjak's Avatar
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    you said in your first post you had bottomed the ski maybe once!!! it only takes once to do damage like this, once chipped the rest will eat away.

    Quote Originally Posted by classic079 View Post
    That's why I am so concerned. I have never once beached it. I always anchor it in like 3ft of water. I guess I will just watch the new pump housing and see if it happens again then worry about it. I will do what you said and get back to you. Thanks!

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