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Thread: Rusty exhaust manifold bolts

  1. #1
    Join Date
    Feb 2004
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    Default Rusty exhaust manifold bolts

    I have a '93 351 HO PCM with rust around the areas where the exhaust manifold bolts to the engine. I'm wondering if anyone has had the experience of the bolts rusting to the point of breaking off the head. Would it be wise to either clean the rust off and paint - or remove the manifolds and replace all the bolts before having a problem.

  2. #2
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    Nov 2003
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    gatlinburg tn
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    Default

    it's hot there. they rust unless you use stainless which is to soft to hold in my opinion.

    you can get a pcm manifold set from skidim with 16 bolts, all gaskets(put them in right) and the riser bolts for 70 bucks or so.

    never-sieze on the threads will keep you from snapping the head off when it comes time to remove them.

    yes, i have broken one of those allen headed buggers. it was overtorqued by the po.
    red right return

  3. #3
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    Thanks for the info on skidim. I let some liquid wrench soak a few minutes on one bolt on each side and removed them. There is some noticable damage on the knurled head and a slight amount just behind it. I would think it might be good for a few more years unless the rust goes deeper than it appears. Haven't decided whether I'm just worrying about something I don't need to worry about - at least not yet.

  4. #4

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    Skidude,

    I know what a problem these corroded bolt heads can be. Have you seen my post "Blowing exhaust 1999 5.8 HO" from the 1st Sept last year.
    Please bear in mind that the problems I had were on a '99 which was only 4 years old at the time. I had a 1987 Ski Nautique 2001 for 14 years and fortunately I did not have any problems with this boat.
    I will be keeping an eye on the bolt heads and will replace them before they corrode too badly. I will also try to extend the life of the bolts by covering them in grease while the boat is laid up.
    2010 Ski Nautique 200 Team Edition Open Bow, Radar Strada
    Dealer: http://www.midlandsnautique.co.uk

  5. #5
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    Mar 2004
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    Default You think you got rust?

    I just went thru this last year with my '93 Excel. The previous owner had run it in salt water and not cleaned it very well. I broke a spark plug off that had rusted into the head. Had to take it to my local boat dealer who had to pull the head, which includes removal of the manifold (The manifold was so rusted, it came off in pieces!). He ended up having to DRILL the manifold bolts out they were so rusted! Hit me in the pocketbook pretty hard! Now this year the opposite manifold has a hole rusted in it, but I'm going to try and remove it myself before sending it back to the dealer. Wish me LUCK!!
    Tomfooter

  6. #6
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    Nov 2003
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    gatlinburg tn
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    Default

    never-sieze.

    tomfooter, if you expect the same outcome. i would cut off the manifold bolts at the heads and remove the manifold. this might give you some extra to bite on instead of the bolts shearing off at the heads. p-b blaster brand penatrating oil works far better than any other product i have ever used. a guy on another site recommended kroil. i can drum up the web address if you need it.
    red right return

  7. #7
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    NigelC, I'm guessing your boat was kept at the dock or otherwise outside to accumulate that much rust so quickly on your '99. My boat has spent a lot of time at the dock. Although its had dehumidifiers to reduce moisture, it obviously didn't stop it completely. I now have it inside, at least for the winter.

    Tomfooter, my last boat, a Mastercraft, suffered from broken bolts and I personally drilled them out with diamond tipped bits. I broke and dulled several bits before getting them out - after several evenings and weekend hours. Both manifolds eventually rusted through and I replaced them. The manifold isn't such a big deal, but I wouldn't wish removing broken bolts on anyone.

    Tryan, thanks for the input on the never-seize products.

    All, I removed a bolt from each side for a better look. I decided to keep the current bolts for now, but removed rust and repainted all around with a 1200 degree hi temp paint containing a rust inhibitor. In hind sight, however, I'd say the better plan is to remove the manifolds. It's then much easier to check the manifolds closely for any spots about to burn through, remove rust, repaint and install new gaskets and bolts. You'll save a lot of time and have confidence that all is well.

  8. #8

    Default

    Skidude, you are right that the boat is kept at the dock during the summer months. My previous '87 (2001) was also kept afloat in the summer. Both boats are religiously kept in a garage over winter.
    Neither boat has been anywhere near the dreaded salt water so I doubt that could be the cause.
    Admitedly the climate here in the UK is not ideal but I would expect the bolts to last longer than they have on my '99. I will look to get hold of some high temperature exhaust paint and see if that helps.
    With the hassles I had removing the manifolds last year it is much easier to keep an eye on the bolts and replace before they corrode too badly.
    2010 Ski Nautique 200 Team Edition Open Bow, Radar Strada
    Dealer: http://www.midlandsnautique.co.uk

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