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  1. #1
    07STX15's Avatar
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    STX-15f losing MPH/RPMs POST RPM kit install

    Guys, Im stuck here. I just upgraded my STX-15f with the Riva RPM kit this past weekend. Finished installed and took t out on the lake to realize I actually LOST power and speed. I know this isnt correct.

    Before the upgrade, my speedodometer read 61-63 consistently (i know thats not GPS speed) around 7200rpms (estimate), but now after the upgrade Im lucky to get the speedo to 58 @ 6k rpms. When I put the ski on the hose, I can reach 8k rpms, but when in the water, the most I get it to is 6k rpms. I followed the instructions as I was supposed to but it seems I may have done something wrong.

    This is where I turn to Green Hulk and its infinite wisdom. Any 15f's out there have any idea what I should be looking for or fixing? Willing to pay to get this thing fixed (since it seems I cant do it correctly). Could it be the pump? Could it be something internal?

    Im losing RPMs, losing MPHs, losing my DAMN mind tryign to figure out what the hell is wrong with the ski. Any suggestions. All assistance is greatly appreciated, but please keep in mind I am an "experienced novice" so I am by no means an expert/ mechanic. Thanks to all in advance for the help. Trying to get it ready for Mudbug!!!


  2. #2
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    What exactly did you install in the kit? does the motor skip or miss? check the blue exhaust coupler from the header to the waterbox, if this is ripped then you will lose serious rpms from that,


    Sean

  3. #3
    Not a ski but we did a head/cam combo on my v8 and timing was off 2 teeth cars ran shit struggled to start, i no its hard but u might have to pull it apart again sorrry bud .

    ---------- Post added at 01:43 PM ---------- Previous post was at 01:41 PM ----------

    Also wat was the lake condition like ur fuel etc best to get a gps only 60 buks

  4. #4
    07STX15's Avatar
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    I installed the free flow exhaust kit w/ primary waterbox mod (new couplers from header to waterbox and new coupler waterbox to exhaust exit), new impeller (Solas 14/21), new (R&D) ride plate, Worx sponsons, stock air filter removed and Riva performance filter (+2 breather filters) installed, plus installed an adjustable shuttle cone assembly.

    Hoelshot is ok but not best. Still throws be back but not anymore than stock. The adjustable shuttle cone assy. isnt the cause because its been installed since I got the ski.

  5. #5
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    How did the prop fit? If its off it could be grinding on the pump housing. I know you said its not the cone but I would try to find a stock one, ill see if I have one I can send you.

    Any weird smells or sounds? How do the spark plugs look? Do you have fresh gas?

    Sean

  6. #6
    07STX15's Avatar
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    Quote Originally Posted by smokeysevin View Post
    What exactly did you install in the kit? does the motor skip or miss? check the blue exhaust coupler from the header to the waterbox, if this is ripped then you will lose serious rpms from that,


    Sean
    The motor did begin to miss the first time I launched. But I chenged the spark plugs (which had a good bit of deposits) and it seems to run good. Sometimes you can hear the idle drop a little, but not enough to kill the ski. The first time I launched I did take on some water (due to a gap in the exhaust exit nozzle not being completely screwed in). It died once or twice before I could get it back on the trailer, but the ski cranked and rode with the water in (keep in mind I didnt ride long, I was already at the dock. i rode it long enough to pull it on the trailer). I dont think it injested water, because the ski ran good after I changed the spark plugs. Before I put the spark plugs in, I turned over the cylinders to see if any water got caught in the block and there was none. So again Imunclear the reason why I am losing power and speed.

    ---------- Post added at 02:15 PM ---------- Previous post was at 02:10 PM ----------

    Quote Originally Posted by smokeysevin View Post
    How did the prop fit? If its off it could be grinding on the pump housing. I know you said its not the cone but I would try to find a stock one, ill see if I have one I can send you.

    Any weird smells or sounds? How do the spark plugs look? Do you have fresh gas?

    Sean
    Prop fit good. No scrapping. Now I do have to confess (i need to be honest to get to the root cause of this) when I took my pump off to change impellers, I took the shuttle cone off and tried to take the impeller out by pulling it out. You see I am used to my older ski (Kawa ZXI 1100) so when you took off the pump the mpeller and shaft came out fairly easily. SO when the STX-15's impeller and shaft didnt come out as the ZXI does, I did bang on the shaft a little with my rubber mallet. Then i realized it doesnt just slide out like the ZXI does. Thats why Im thinking I may need to rebuild my pump.

    ---------- Post added at 02:17 PM ---------- Previous post was at 02:15 PM ----------

    [QUOTE= I know you said its not the cone but I would try to find a stock one, ill see if I have one I can send you.

    Any weird smells or sounds? How do the spark plugs look? Do you have fresh gas?

    Sean[/QUOTE]

    That would be awesome Smokey. No to the fresh gas it has been in there for a little while, although I do put Stabil in every tank of gas I put in it.

  7. #7
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    I would drain the fuel, change the oil now do not run it again without it, change the pump bearings, you have probably messed up the bearings in the pump by hitting them. Other than that check the plugs again and run through the electrical harness connections to see if they are corroded, clean them if they are.

    Try that and let us know,

    Sean

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