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  1. #1

    2005 STX-15F Continually needing new spark plugs

    Hello,

    I own a 2005 STX-15F with 210 hours. So far this ski has been great. I have noticed though that this ski goes through spark plugs way to quickly. I first changed the plugs around 70 hours, then around 130, 170, 200, and now, 210. Each time I have had to replace the plugs because it would not start up. As soon as I popped the new plugs in it would start right up and run. I can tell when it is getting close to needing new plugs because it will start to have hesitant cold starts with a rough idle. Once the engine is warm it will start right up and idle fine. Each time I pulled the plugs they seemed to look okay, not great. Just yesterday when I pulled the plugs I noticed what might have been a tiny bit of oil on a couple of them. I do a LOT wakeboard pulling behind the ski, and a lot of cruising around 30 mph. Any ideas/suggestions would be greatly appreciated! I am tired of buying new spark plugs! Thanks


  2. #2
    Fat Man, Little Boat Region8Ultra250X's Avatar
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    sounds like its loading up causing it to foul plugs

  3. #3
    Could you explain what "loading up" is exactly? Sorry for my ignorance

  4. #4
    Fat Man, Little Boat Region8Ultra250X's Avatar
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    Quote Originally Posted by tylercnewport View Post
    Could you explain what "loading up" is exactly? Sorry for my ignorance
    the fuel isnt burning causing it to load up on fuel and foul. probably a result of the extended low speed/low rpm cruising. seems like your changing plugs at 10 hours now. my suggestion would be to put a fresh set in and ride it harder than you normally would.... i.e. above 30mph and limit or dont pull a wakeboard or skier. do this for 10 hours and see how they compare to the set you pulled out.

    this should give you an indication as to whats going on in the motor. if they clear up it may just have had to have been ridden harder for a bit. if they dont it could be a number of things.

    shoot a pm to smokeysevin. hes a 15F guru on this board

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  6. #5
    Okay thanks I'll give it a go.

  7. #6
    Been around for years...seen it all Kawi-Guy's Avatar
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    Which spark Plugs are you using ? Have you tried the NGK CR9EIX Iridium plugs?

  8. #7
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    Thanks for the kind words, Mr.Dan. I doubt its fouling the plugs because of the load, I have almost 70 hours on my last set of plugs (just to see how long they would last) in my 12f and that spent most of its life towing a wakeskate and it never had problems fouling plugs. Please post pictures of the plugs if you can, check the compression, check the fuel pressure.

    I have a few questions for you,

    Do you ride in salt water or fresh water?

    When you put the ski away do you flush it and if so how (be specific please)?

    How long does the ski sit between rides?

    What type of fuel do you use?

    Do you have an aftermarket intake or exhaust setup?

    Does the ski smoke at all (smoke not steam from the wet exhaust)?

    Remove the plastic cover of the exhaust tip and clean the inside of the tip, leave this off and ride a few times then see if it gets sooty or black.

    Before you put the ski up, try running at full throttle for a few minutes then put it up, if the plugs are fouling because its loaded up (which is possible) this will help out.

    There are 2 temperature sensors that have new part numbers, this helps in starting while hot. They are not terrible to replace, check the thread in my signature for the part numbers.


    please quote my post and reply in the quoted text box but in red color.

    We will figure this out,

    Sean

  9. #8
    Quote Originally Posted by smokeysevin View Post
    Thanks for the kind words, Mr.Dan. I doubt its fouling the plugs because of the load, I have almost 70 hours on my last set of plugs (just to see how long they would last) in my 12f and that spent most of its life towing a wakeskate and it never had problems fouling plugs. Please post pictures of the plugs if you can, check the compression, check the fuel pressure. I have yet to check these, I'll try to get it done by next week.

    I have a few questions for you,

    Do you ride in salt water or fresh water?
    Fresh, never been in salt water
    When you put the ski away do you flush it and if so how (be specific please)?
    No, I have only flushed it once, when I winterized it
    How long does the ski sit between rides?
    In the summer (May-Aug) I ride it very often, usually 3-4 days a week. The most it will sit is a week. I usually put 100hrs a summer on it. After August, it goes to dry storage
    What type of fuel do you use?
    87 octane from Chevron, I fill up portable gas tanks to fill the ski
    Do you have an aftermarket intake or exhaust setup?
    Everything is bone stock
    Does the ski smoke at all (smoke not steam from the wet exhaust)?
    I have maybe only seen some smoke maybe once or twice, for shorter than 10 seconds
    Remove the plastic cover of the exhaust tip and clean the inside of the tip, leave this off and ride a few times then see if it gets sooty or black.
    Ill try to get this done next week as well
    Before you put the ski up, try running at full throttle for a few minutes then put it up, if the plugs are fouling because its loaded up (which is possible) this will help out.
    Will do! Gotta love doing 60 across the lake
    There are 2 temperature sensors that have new part numbers, this helps in starting while hot. They are not terrible to replace, check the thread in my signature for the part numbers. Before I let go of the cash for this, is this really worth it?


    please quote my post and reply in the quoted text box but in red color.

    We will figure this out,

    Sean
    Thanks! Just to let you know, at 210 hours I replaced the plugs this time with CR8EK rather than the CR9EK's. I figured maybe a hotter plug could help. What do you think?

  10. #9
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    It wont hurt on a stock ski, I ran them on my race ski while testing it and it was fine. When you put the ski away rev the engine to about 5500 rpms a few times, this will blow most of the water out of the exhaust and help prevent the plugs from rusting.

    Sean

  11. #10
    slothman's Avatar
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    Quote Originally Posted by tylercnewport View Post
    Hello,

    I own a 2005 STX-15F with 210 hours. So far this ski has been great. I have noticed though that this ski goes through spark plugs way to quickly. I first changed the plugs around 70 hours, then around 130, 170, 200, and now, 210. Each time I have had to replace the plugs because it would not start up. As soon as I popped the new plugs in it would start right up and run. I can tell when it is getting close to needing new plugs because it will start to have hesitant cold starts with a rough idle. Once the engine is warm it will start right up and idle fine. Each time I pulled the plugs they seemed to look okay, not great. Just yesterday when I pulled the plugs I noticed what might have been a tiny bit of oil on a couple of them. I do a LOT wakeboard pulling behind the ski, and a lot of cruising around 30 mph. Any ideas/suggestions would be greatly appreciated! I am tired of buying new spark plugs! Thanks
    Are they black or more oily looking ? The ski might be running rich, causing them to foul. If it's smoking could be valve seals or piston ring blow by. Maybe a small amount of oil is getting past the rings causing the plugs to foul?

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