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  1. #1
    Top Dog west_coaster's Avatar
    Join Date
    Apr 2005
    San Diego CA

    Rotted exhaust manifold post mortem

    My ski suffered from the rotted manifold problem many of us have had. It's all fixed up now, but I thought the old rotted one was interesting.

    I smacked the rotted part off with a hammer, and this is what was exposed. Seems to me that a lot of sand and debris settled in the area of the #1 cylinder. In fact it's packed solid, no water can get in there. Rest of the inside of the manifold looks like it's been run in salt water, which it has, but isn't anywhere near as bad as this area.

    My guess is the ski was run through a lot of sand in the past, and poorly flushed. Over time this packed the area and due to heat it rotted away. You can see the spot at the bottom where the exhaust actually went through the inner water cavity and then through the outer walls.

    Last few times I used the ski, it's only produced about 5800 RPM, and the very last time it would take 5-10 seconds to go from idle to full power which was 5000 rpm. Also, the last few times I've used it I had to free up the turbo as it was "frozen". Now I understand that the exhaust part of the turbo was flooded with water, and under pressure was probably pushing water through wherever it could go. Obviously I had a ton of water in the oil. When it sat, I think the exhaust side of the turbo rusted and thats why it locked up.

    With everything apart, I noticed the wastegate arm was getting sticky, most likely from the water being pushed up the bushing.

    With everything apart for 2 months, I used penetrating oil on the wastegate arm bushing, then used some gas to clean it out. After drying for a few weeks, I added some high temp lube and the arm works very freely. I'll keep an eye on it and lube it after every use.

    I also took the exhaust side off the turbo and used a wire brush on a dremel to clean it up inside and out. Used some engine paint to make it look nice.

    Ski goes out tomorrow for a test ride.

    While I like the Honda, I'm never going to wait months for a part again, and miss prime riding season. I'll be selling this and getting one of the new 300 HP rides with all the bells and whistles. I keep reminding myself this is a 12 year old toy.

    Last edited by west_coaster; 09-23-2017 at 09:26 PM.
    05 F-12X

    I'm on the drinking diet. I lost 2 days already.

  2. #2
    PWCToday Guru NunoP's Avatar
    Join Date
    Apr 2010

    Re: Rotted exhaust manifold post mortem

    Great Post.
    I wonder how many of us are being affected by this.

    What would be the best way to clean it before it colaps as yours?
    2004 F12X

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