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  1. #1

    2006 STX-15F exhaust questions

    Hey everyone, hope to get a little advice. I am a very experienced mechanic, but new to pwc's. 2006 STX-15F with about 100 hours on it. To my knowledge never been in salt water. Had a small leak when leaving it in the water overnight. Found the leak, coming from the blue coupler area. I'm thinking no biggie, a $14 part. Tore it apart today and found the tiny hole, it was in the bottom of the waterbox. Now I have a few questions. See the pics below the questions.

    1. Why would this continually leak water? Since the exhaust tubing loops above the waterline between the two mufflers, I would think that it would leak until it drained the waterbox then stop. Was it just continually pulling water through the engine as it sat overnight?

    2. There is a good bit of corrosion on top of the exhaust manifold pipe. I'm assuming that the best thing to do is just replace this piece while I am in there right?

    3. Can the pin hole and the seam around it be welded by a good aluminum welder or is it best to just replace it? Those things are expensive, is there a good alternative to the $700 factory part? I'm not afraid to spend the money if it is necessary, but if there is a good alternative I'm open to suggestions.

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  2. #2
    It leaks because cooling water gets dumped in there and it collects and seeps out of the hole. Weld the crap out of it, free up the rings on the stinger in their grooves and rock and roll.


  3. #3

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    Not trying to hijack the thread. But can someone explain why there are 2 waterboxs on exhaust, and is removing one beneficial or does it create possible issues by doing so? I notice alot of talk of free flow exhaust etc, but worried about water working back into motor from the rear, lake etc.

  4. #4
    RLACEMAN's Avatar
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    2 waterboxes to control noise. The newer 2009 & later only have one, but have smaller diameter pipe to control sound. I had a 2006 & bypassed the second waterbox to see what difference there was if any. The ski was noticeably louder, too loud to drive in my opinion & the increase in performance, (rpms) was minimal, about 1/2mph increase, not worth the extra noise. For post above I would also try welding old waterbox first, also start looking on the internet occasionally the primary waterboxes show up for sale.

  5. #5
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    Quote Originally Posted by Ryanfunfishing View Post
    Not trying to hijack the thread. But can someone explain why there are 2 waterboxs on exhaust, and is removing one beneficial or does it create possible issues by doing so? I notice alot of talk of free flow exhaust etc, but worried about water working back into motor from the rear, lake etc.

    but that's exactly what you're trying to do....

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  7. #6
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    Quote Originally Posted by rmoore0852 View Post
    Hey everyone, hope to get a little advice. I am a very experienced mechanic, but new to pwc's. 2006 STX-15F with about 100 hours on it. To my knowledge never been in salt water. Had a small leak when leaving it in the water overnight. Found the leak, coming from the blue coupler area. I'm thinking no biggie, a $14 part. Tore it apart today and found the tiny hole, it was in the bottom of the waterbox. Now I have a few questions. See the pics below the questions.

    1. Why would this continually leak water? Since the exhaust tubing loops above the waterline between the two mufflers, I would think that it would leak until it drained the waterbox then stop. Was it just continually pulling water through the engine as it sat overnight?

    2. There is a good bit of corrosion on top of the exhaust manifold pipe. I'm assuming that the best thing to do is just replace this piece while I am in there right?

    3. Can the pin hole and the seam around it be welded by a good aluminum welder or is it best to just replace it? Those things are expensive, is there a good alternative to the $700 factory part? I'm not afraid to spend the money if it is necessary, but if there is a good alternative I'm open to suggestions.

    unless you have a really good aluminum welder at your disposal, I'd use some jb weld to fill in all of the corrosion issues and file it into shape. An amateur will damage the part

    as stated, those rings grooves on the Mikey mouse sealing system have to be cleaned up big time

    I'd put some anti size on it for assembly. without fail get new sealing rings and wire brush the inside of the mating assembly

    wait till you try to put it together..be ready for some pain. wear gloves

    in my book these are just as bad as a seadoo two stroke where the expansion pipe joint was spit

  8. #7
    I'm just going to replace the pipe. Apparently the sealing rings on these things are kind of finicky and that's fairly corroded. The pipe is the cheap part at $300. I do have a good aluminum welder to look at the water box. My concern is that if the corrosion came from the inside am I just putting a band-aid on that part and it will spring another leak in a different spot? Weird thing is that the entire inside of the area around the pin hole looks fine. Looks like the corrosion ate in from the outside, which is the opposite of what I would expect. Your thoughts??

    Two additional questions

    1. What is the light colored rubbery sealant used on the exhaust manifold gaskets? When I get the new gaskets will they come with this sealant or do I need to get some?
    2. The service manual and lots of forum posts say to use paper tape to hold the sealing rings, but it doesn't say anything other than that. Are they talking about masking tape or something else that's higher strength?

  9. #8

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    The pipe looks pretty good. If you clean out the grooves and install new rings, you should be OK. The bigger concern would be holes on the top and bottom of the fat part of the pipe end, but your pic doesn't show it. Replacing it is not a bad idea, especially if you plan to keep the ski.

    I'd replace that waterbox. You can try fixing it, but you'll only be putting off replacing it. It might last a ride or a season, but you'll be dealing with another leak sooner or later. They also tend to get corrosion on the bottom, where the waterbox rests on the padding in the hull... salt gets trapped.

    The gaskets come with that coating on it. On some motors, the gasket doesn't even have the coating. I've seen both.

    Use masking tape to compress the rings into the grooves. The end of the waterbox will slip easily over the rings. Then the masking tape will burn off when you ring the motor, and allow the rings to expand.

  10. #9

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    This is a common issue on these unfortunately, more so in saltwater no matter how well you flush. You've already said the fix, replace the "Stinger" part of the pipe and put 2 new rings on the end.(They are the same rings the Piston uses oddly enough).. If you can get the water box Tig welded and get a new coupler you should be good to go.Although if you can find a box in better shape that's the way to go.. When I had my older 12F I would check it every year, clean and reinstall as part of the pre season checks.

    Also check the water pipe under the intake manifold. The end tends to rot where the rubber hose connects. The new piece was redesigned so that doesn't happen.

  11. #10

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    Here is how I would fix that., YMMV. Cut that piece with the pin hole off, take note of the location and angle (this is what a small fixture plate is for). Find a piece of pipe or round stock to size. Spin it up on the lathe to get the dimensions required to match the old one. Fire up the Miller dynasty 300DX and weld away. I might be doing this soon to a water box with the same issue.

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