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  1. #1
    deksea's Avatar
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    is it normal for water to run through the exhaust manifold passages 04 STX 12F

    Hi Everyone

    I have a 2004 Kawasaki STX12F and recently started getting water in the bilge. Turns out the underside of the lower section of the exhaust manifold had two pin holes in it that was allowing cooling water to leak from the cooling water passage of the manifold into the engine compartment. I removed the manifold, and I hooked one of the cooling supply hoses to a water source and ran water through the manifold to precisely locate these pin holes as it was very difficult to spot them by visual alone. Running water though the manifold did the trick as far as spotting the holes, but I also noticed that while water flowed out the ends of the ports at the head mating flange (as it should) water was also draining out through the inside exhaust passage and out the end of the manifold pipe that connects to the water box. Is this normal? Reviewing the cooling flow diagram in the service manual does not show any water flow that runs down the exhaust passage of the manifold, it shows all of the water that is supplied by the two cooling water connections at the manifold flowing out those ports into the head. The concern Ive got is that perhaps there are some additional corrosion holes in the manifold cooling passage that are leaking into the exhaust passage that might to continue to open up and starve the head of critically needed cooling water.

    Anyone know the answer? Thanks!!
    Last edited by deksea; 04-24-2017 at 09:23 AM.


  2. #2
    DavidR's Avatar
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  3. #3
    deksea's Avatar
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    DAVE

    This helps, thanks. The debate in this string was on flushing, but it appears the consensus was that water does NOT run down the inside of a healthy exhaust manifold. I have ordered a replacement manifold, It arrives in a few days. I'll know the answer for sure then because I'm going to test it, and I'll post back for the record.

  4. #4
    deksea's Avatar
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    OK, here's the definitive answer: Water is definitely NOT supposed to come out the exhaust passage of these 12F 15F manifolds. Here's what my old manifold was doing:



    The "new" ebay manifold arrived yesterday and I hooked it up to the hose and of course the only water that came out of it was through the top of the ports at the head mating flange. So I took the old manifold apart, set the lower half on its end, and put the water to it:



    I figured maybe I could look inside the exhaust passages and see where the leak was coming from. It didnt take much looking to find the problem:














    If you look closely, you can see the water leaking inside one of the quadrants in the photo on the left. The photo on the right is a shot straight down the passage of that quadrant. This is a problem that probably would have gotten much worse very quickly and a few months from now I would have been wondering why I wasn't getting any cooling to the engine when everything appeared to be working correctly. And again, the only reason I discovered this problem is because I was filling the manifold with water to spot leaks on the outside of the manifold and just happened to notice water running out of the inside of the manifold as a result. I got lucky this time. I've recently started to have idle problems with this ski. Perhaps its from too much exhaust back pressure from all that extra water loading up in the exhaust system. I'll know soon enough.
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  5. #5
    wow thats serious corrosion...thanks for sharing....

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  7. #6
    steve45's Avatar
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    Just curious, are you running in salt water? If so, do you flush it after each outing?

  8. #7
    deksea's Avatar
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    Hi Steve

    Regarding your questions (and hold on to your hat):

    The ski is run in Chesapeake bay and associated rivers, so certainly not as much salt as you'd see out in the ocean, but there's still enough to do some damage if ignored. I just recent received this ski FOR FREE from a fairly wealthy friend who, despite his wealth, was going crazy with the never ending and increasingly large repair bills from the stealership to keep this ski operating for his kids. Nobody likes to get screwed. And so when the next huge repair estimate came in he said "come get this thing away from me". And of course I did. And now to your last question:


    It's a 2004 with about 125 hours on in fairly good cosmetic condition, but in all the time it was operated before I took possession of it (11 years) NOT A SINGLE TIME WAS IT EVER FLUSHED. Not once. For those who may be curious as to what happens with a ski that operates that long without a flush, (I know some of you can take a very good quess at the probable failure points) I'm going to post a separate message of my trials over the last two years to bring this ski back to life. And BTW, now that I don't have all that extra water running through the exhaust system, my exhaust back pressure theory above was apparently on target. The ski now idles perfectly. No excessive backpressure to confuse the computer anymore. But that has unmasked yet another problem with the ski that I am going to put up a separate post for. Stay tuned......



    Dave

  9. #8
    Pain is fear leaving your body.... rlovebk's Avatar
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    Valves/guides may be thrashed. Make sure and use anti-seize on spark plugs.
    Maybe this was done and is bill(s) your friend spoke of and why it cost arm/leg/2 fingers off other side.
    Any parts needed motor-wise I may be able to help.
    Output cover is probably toast. (Hopefully not)
    Good luck sir. Good pics and good find

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  11. #9
    deksea's Avatar
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    rlovebk

    They say nothings free. I suppose so, and I knew going in that this ski would need lots of TLC initially. The last two years have been a crash course for me on jet skis and the 12R/15R in particular. This forum has been extremely helpful to me in getting smart on these systems fast. I'm no stranger to mechanical systems, but jetskis are their own breed, of course. I'll tell you all about it in my upcoming "no flush" story. Warped heads, clogged and corroded engine components, swelled wear rings, etc. etc. etc. You could probably write your own version based on just your guesses and be 95% on target with what actually happened.


    DK

  12. #10
    RLACEMAN's Avatar
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    Did you noticed a reduction in full throttle rpms with this "leak", or an increase after it was repaired, a couple years ago I experienced a slight loss in rpms for no apparent reason & have never been able to get them back & have heard about these corrosion issues with the exhaust. For me its too much work to disassemble the exhaust system just to check it.

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