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  1. #1

    06 STX-15F running horrible

    Ok, so some background info: Bought the ski new in 2006 and ran it about 14 hours in salt water and 14 hours in fresh water total time on it is 28 hours. No mods, so its completely stock. I stopped riding it in 2008 and it sat for 2 years before I cranked it up again. I had to replace the battery as well as the spark plugs but got it running back in 2010 but didn't ride it that season. After that I committed the big no no and let it sit for another 3 years. I let it sit with gas in the tank and of course it has since evaporated and now is dry. Recently, I decided to get it back into commission and with no surprise it wouldn't start. So I put a new battery in it, changed out the oil with AMSOil, put fresh gas with seafoam added, checked the fuel rail and injectors and changed out the fuel pump and it started. However, I took it out to the lake to test it out in the water this past weekend and had a few issues.

    First it seemed to be running fine but felt bogged down whenever I pressed down on the throttle trigger. Then it would slowy accelerate and then decelerate, the closest thing I could relate it to is it felt like a car when it downshifts. Finally I decided to get after it and see if I could reach the top speed I did before which is ~58-60 MPH without GPS. No such luck, it got to about 50 MPH and then gradually the speedo fell to 47 then to 45 then just tapered off to where I couldn't even move while giving it the throttle, so I ended up only being able to idle. I turned it off and that was a big mistake because it then wouldn't even crank the motor.

    When I got it home, I pulled the plugs and 2 of the 4 were fouled, one the insulation was broke up and the other had one of the prongs bridged to the electrode. Looks to me as if it was running lean for a bit, I have to say that once the ski completely bogged down into idle it was running rich because I could smell the gas from the exhaust but no smoke. I have attached a few pics of the bad plugs. The other 2 looks normal with some blackening but the gaps and all looked fine.

    I poked around the forums and read a few posts that noted some of the same symptoms such as: skis running at high RPM's and getting bogged down and they were having exhaust leak problems and another post said the owner had to replace spark plugs frequently. I haven't checked for that yet but plan to, after I changed out the spark plugs it did run again but the condition of the plugs and the fact that it was running lean concerns me. I probably need to check the compression as well and plan to do that too. I need to get it back into the water to see if this happens again.

    If anyone thinks that they might know what is going on that would be awesome, I know Smokey is the guru when it comes to the STX's so I am definitely waiting for him to repsond. Anyway as always thanks in advance to any responses.Click image for larger version. 

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  2. #2
    steve45's Avatar
    Join Date
    Feb 2008
    My guess would be lean from crap in the fuel, causing detonation, wrecking the plugs and probably the pistons.

  3. #3
    I hope not, I put new gas in it maybe some leftover residue from it sitting? I was hoping the Seafoam would do the job, but I hope the pistons aren't wrecked. I guess I will have to get it back onto the water to test it out. I just don't like the way that busted up plug looked.

  4. #4
    steve45's Avatar
    Join Date
    Feb 2008

    DO NOT RUN IT ANYMORE until you determine what damage has been done. You may have pieces of junk floating around inside that will destroy what's left of it.

    Gas doesn't just disappear, especially when it's got ethanol in it. It reacts with various fuel system components and forms gum and other crud that impede fuel flow.

    I seriously think the head needs to come off and see how bad the damage is. Also, the entire fuel system needs to be disassembled and cleaned. SeaFoam can only do so much.

  5. #5
    Ok Steve, I'll take your advice and break down the fuel system along with taking the head off and check it out. Thanks for your response, that is why I like this forum so much!

  6. #6
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
    Join Date
    May 2008
    Pull the plugs and check the compression.


  7. #7
    Quote Originally Posted by smokeysevin View Post
    Pull the plugs and check the compression.

    That's on my list, thanks Smokey.

  8. #8
    So I pulled the cylinder head cover and didn't really see anything besides a little spot of rust on the camshaft chain. Anything special that I am looking for? Thanks.Click image for larger version. 

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  9. #9
    steve45's Avatar
    Join Date
    Feb 2008
    Not the head cover, the head--but as Smokey said, do a compression test first.

    If compression is good, you might have dodged a bullet.

  10. +1 by:

  11. #10
    LOL, I'm a dufus...

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