Rotted exhaust manifold post mortem

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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

  3. #3
    Frequent Poster
    Join Date
    Jul 2012
    Apex NC

    Re: Rotted exhaust manifold post mortem

    Be careful thinking a new ski won't keep you from missing the summer riding season. With the new one you will be waiting for someone else to fix it under warranty. Might want to keep this one and get a new one.

  4. #4
    PWCToday Guru skidoc's Avatar
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    May 2012

    Re: Rotted exhaust manifold post mortem

    We will have a New and In proved Honda Exhaust manufacture Soon.
    Jet Skis International
    Brian Brocksmith
    Free Aquatrax Tech support

  5. #5 Is My Home Away From Home JR IN JAX's Avatar
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    Jun 2003
    Blog Entries

    Re: Rotted exhaust manifold post mortem

    Quote Originally Posted by skidoc View Post
    We will have a New and In proved Honda Exhaust manufacture Soon.
    Let me know when it comes out.
    Honda Pilot NAVI
    F150 4x4
    3 '06 F12Xs
    2 CR80s
    1 XR100
    2 PW50s
    1 Vento Phantom 150
    1 Honda SHI 150
    '98 Allison Grandsport/Merc Racing 300 XS
    Jax. Fl.

    "Confidence is the feeling you have right before you fully understand the situation"

    "The automated aircraft of the future will have a crew of two; a pilot and a dog".
    The pilot is tasked with feeding the dog. The dog is to bite the pilot if he touches the controls.

    "Any ship can be a minesweeper,,, once".

  6. #6
    Top Dog spatera's Avatar
    Join Date
    Jul 2006
    South Ga

    Re: Rotted exhaust manifold post mortem

    Tell us more.
    07 Honda F12X Saphire Blue
    MacBoost, Large intercooler, solas intake grate and impeller.

    03 Honda F12X Red

    Jim's Alpha Boost kit, H2O ECU Modulator, Large Intercooler, Solas intake grate and Impeller

    05 SeaDoo GTX 4-tec Supercharged

    Used to have:
    98 GP760, 97 GTX Sea Doo, 97 GP1200, 02 Honda F12X, 2-03 Honda F12X,

    Need to have:

  7. #7
    PWCToday Newbie
    Join Date
    Jul 2017

    Re: Rotted exhaust manifold post mortem

    Yes Brian please tell us more about it

  8. #8
    PWCToday Regular
    Join Date
    Apr 2018

    Re: Rotted exhaust manifold post mortem

    Do you still have the rotted manifold? Do you want to get rid of it?

  9. #9
    PWCToday Newbie
    Join Date
    Jul 2011
    Lanexa, VA

    Re: Rotted exhaust manifold post mortem

    Quote Originally Posted by mattjw76 View Post
    Do you still have the rotted manifold? Do you want to get rid of it?
    Shoot, wish you would have said this last week. I just tossed a rotten one. Wasn't as dramatic looking as the original poster's part, though. Sorry.
    Last edited by Lightningtruck; 04-18-2018 at 12:20 PM.

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