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  1. #1
    785xp's Avatar
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    Major Assistance needed with STX-15F

    2004 Kawasaki STX-15F

    I had the engine rebuilt over the winter replacing everything(Crank, pistons etc). It had 64 hours on it at the time. I had the valve clearance checked by the mechanic that rebuilt it. They were fine. Spring came and I went though the break in process. During the break in, I did get it up to 61 mph on the speedo a couple of times for a very short duration. At about 72 hours, I was out riding it and was trying to get a top speed out of it when I ran into some trouble. The speed started to drop as well as the RPM’s. I let off the throttle and it stalled. Couldn’t get it started again. Got it towed to shore.

    Took off the coupler cover and noticed that the coupler was jammed together. Took off the ride plate and the pump and to my surprise when I pulled off the pump, the prop stayed on the drive shaft. Pulled it off. The pump shaft was damaged and once I took the pump apart, it was apparent that it would need a rebuild. Tried a couple of times to start the ski with no success. On the evening we were going to head down from Canada to Tennessee, I tried it one last time and it started. I decided to take it with us to wrench on since I had a new pump and prop meeting me there from Riva.

    Down in Norris, put it back together and took it for a ride after doing a compression check. The RPM’s were just a couple of bars above 6000 and the top speed was about 53 mph. Started to think that maybe the drive shaft was bent and that was what caused the prop to spin off. It was either that or the shop that installed the Skat prop that was on it didn’t tighten it enough.

    When I got home I changed the oil and installed an Air Intake figuring that maybe there was too much oil in it causing the low rpms. I had it out to Lake Erie a couple of times in some very big waves and it ran great but I never had a chance to get any top speeds out of it. Last weekend I had a chance to take it to a very flat lake and run it. RPM’s again were just above 6000 and top speed on the speedo(and GPS) was 52mph. There was no vibration so I didn’t think it could be a drive shaft, but I am also used to 2 strokes. I had it out 4-5 times taking the kids for rides. JayZ showed up on his XP so we decided to go for a tour. 15 minutes into the ride I was a WOT when the RPM’s and speed started to drop. I was going 53 mph then it dropped slowly down to 49 mph. I let off the throttle and it stalled. Couldn’t get it started again. Wore out the battery. Towed all the way back to the cottage.

    I figured it was the pump again, but tonight I took off the coupler cover and everything looks fine. Tried to start it by boosting the dead battery with my truck. It turns over very slow but does no start. With the plugs out it spins with no problem. The plugs look fine.

    Any input would be appreciated. The closest dealer to me is 2 hours away and I doubt they can help me.


  2. #2
    Formerly Ultra250 TN Aquaholic6801's Avatar
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    Hey Man whats going on besides the problems?

    Im sure you have checked the plugs and the throttle adjustments?
    I have also been hearing of cam timing chains having problems.I havent had any problems with my 15f, but ill call a mechanic buddy of mine tomorrow(sunday) and see if he might have some insight.

  3. #3
    785xp's Avatar
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    I haven't had much time to ride since the baby came in June. The XP has been on the trailer most of the summer. I had a lot of fun riding the 15F in the big waves of Lake Erie. So much fun that I didn't take the XP off the trailer. That says a lot since I have never found a three seater that I really liked. I am planning on hitting Lake Huron on the XP on Monday, it is a holiday up here.

    The plugs were new and the throttle was opening wide. Also the way that it shut down leads me away from that. I am wondering if when the impellor came out of the pump and pushed the coupler into the engine that it damaged the crank position sensor or a crank bearing. Before I pull the engine again and take it to my mechanic to take apart, I want to exhaust all possibilities.

    Another thought I had was could this be happening from a bad battery. It is a Yuasa closed cell battery, but it would be 3 years old.

  4. #4
    785xp's Avatar
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    Throw some ideas at me guys.

  5. #5
    Formerly Ultra250 TN Aquaholic6801's Avatar
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    I finally got to talk to my tech buddy, he said to check the big bearing closest to the stator, and also to check the blue silicone connector on the exhaust box,he said he has had 2 of them here recently that when he put them back together that they developed a small split and coundnt see it till he removed the air box, spilling exhaust fumes into the engine compartment. hope this helps

  6. #6
    785xp's Avatar
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    It was the bearing next to the stator that had signs of wear when we tore it down. The original reason for the engine going was water ingestion, but with the prop being loose, it was taking its toll on the bearing. I replaced all of them as well as the crank. I was hoping the loose prop didn't damage it again. I hope to have time this weekend to put a good battery in it and try to start it again.

    I rode it with the seat off when I was low on RPM's to make sure my exhaust gasket wasn't leaking water. I would have seen a leak at the blue silicone connector.

    I will speak to my mechanic next week to see what he thinks. He knows his stuff, but just hasn't worked on any watercraft. I have a feeling the engine is coming out again for a teardown. Hopefully the only costs incurred are a bearing and gasket kit plus labour. Our summers are too short for this stuff.

    Maybe you can clear up a question I have regarding the RPM gauge. On mine, there are 3 bars between each number. I am going on the assumption that each is worth about 333 rpms. I was seeing 6 plus 2 bars before it gave out. I think it should have been at 7 plus 2 bars.

  7. #7
    Formerly Ultra250 TN Aquaholic6801's Avatar
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    Mine shows 2 to 3 bars over 7 when WOT.Pull the air box just to be sure, because he said that he had run them with the seat off also, but I guess being that close to the intake it was sucking in the exhaust, I dunno.

  8. #8
    785xp's Avatar
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    I forgot to mention I installed an intake cone so the stock box is gone. It makes sense that being down 1000 rpms cost me 10 mph.

    Right now, the mystery is why it won't start. I should have time this weekend with a freshly charged battery.

  9. #9
    785xp's Avatar
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    Charged the battery, put it in, started up first try, no problem. This thing is confusing me. I haven't had a chance to take the pump off yet for a look, but I will try to this week.

  10. #10
    PhilnEdee's Avatar
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    Man...nothing worse than being at the lake and running into the Let it sit for a little while, maybe it'll start then" problems...smells like Gremlins!

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