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Exhaust Manifolds

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Old 07-31-2007, 02:55 PM
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Default Exhaust Manifolds

I am trying to have my exhaust manifolds replaced. The problem, is one is so bad it has a hole in it from corosion. The shop it is at is used to only fresh water boats. Any advice for getting the manifold off of the head? I know the bolts will probably break. Would cutting the heads of the bolts off and then deal with the studs be the easiest? Any help would be great. Thanks
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Old 07-31-2007, 03:20 PM
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My freshwater mechanic looked at a boat for me with the same problem. He said (with a moan) worst case he would have to pull the motor and get a small hacksaw to cut through the bolts. I would spray it with W-D40 for a week or two before I undergo that kind of work. I'm sure there is something else you can spray that will help.
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Old 07-31-2007, 03:21 PM
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I had to cut the heads of the bolts off to get mine off but i also replaced the heads so i did not have to worry about the studs. I used a air grinder with a carbid tip one cone shaped and one round. It took a while but got them off.

You can try heating them up and use a gator grip. Or keep going down a size on the socket and beat it on wit a hammer untill you can break them loose.

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Old 07-31-2007, 03:34 PM
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Try Kroil instead of WD-40
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Old 07-31-2007, 03:40 PM
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Quote:
Originally Posted by GOFASTJUNKIE View Post
I am trying to have my exhaust manifolds replaced. The problem, is one is so bad it has a hole in it from corosion. The shop it is at is used to only fresh water boats. Any advice for getting the manifold off of the head? I know the bolts will probably break. Would cutting the heads of the bolts off and then deal with the studs be the easiest? Any help would be great. Thanks

We have purchased liquid nitrogen in the past in a thermos from a welding supply store. Put it like a sports drink container that has the built in flexible straw about 3/8 dia.

The cold frost / air/ gas comes out of the straw.

Aim the straw on your bolt and let it get good and frosted up.
It will shrink the bolt, then start to turn it out.

If you buy this stuff, have your sports drink container etc.
already to go, so you don't lose the maximum strength while your screwing around.

Cougarman
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Old 07-31-2007, 03:55 PM
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cut the head of the bolt/bolts off with a dia grinder. heck you can even use a dremel tool. bring a lot of wheeels for the dremel... then, screw in SST(or steel) studs with anti-seaze on them. slide the mainfold on and off.
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Old 07-31-2007, 03:57 PM
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I also have 2 (two) sets of frresh water BBC merc exhaust manifolds I can sell you. They come with the elbows.. Put on new gaskets and away you go. can ship out this week....
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Old 07-31-2007, 08:34 PM
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Thanks for all of the ideas. I called the shop earlier and I can tell they don't want to mess with it. They are claiming that the manifold has "welded" itself to the head. They also would "have to bring someone in with a torch" to cut the bolt heads off. I am going to drive the 2.5 hours tomorrow and pick the boat up and bring it home and try to fix it this weekend. I am really curious to see how two different metals have "welded" themselves together. The way I figure it, is if the manifold was the hot, the head gasket would be bad. I guess I have my work cut out for me......I will try to post some pics this weekend......Thanks again.....
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Old 08-01-2007, 02:09 PM
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I had the same problem with a boat that I bought...I took nuts and laid the nut over the eroaded stud and filled the center of the nut with weld, basiclly welding a new nut to the old stud. You have to clean the old stud good, turn the welder up. The stud will either unscrew or may break the head off. Hope this helps ya. When I took the heads off I had the same problem and welding the nuts did not work, and I had to cut the heads off with a torch, but make sure to fill the bilge with water....
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