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  1. #1
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    Exhaust riser leak, how do manifolds look?

    I had a leak on the outside edge of my exhaust riser, not bad but little squirts under full throttle. Motor got pretty hot a couple months ago due to a break in my perko fresh water flush intake (old design) which is where I suspect the leak originated.

    Finally got it off (rear bolts were tough angles) and cleaned up.
    Concerned if there will be any problems due to corrosion, especially on the front fresh water ports? Definately thinned a little, probably 3/16" at the thin points.
    Exhaust manifold side looks pretty flat, maybe a slight pit or two. I have not cleaned up the riser yet.

    A little trouble locating the gasket too. 91' Indmar 454 BB, narrow risers 53-1020. Measure 7" long exterior, 5" inner. 4 3/4" wide exterior, 1 3/4" interior.
    Cant find a cross reference in Land n Sea for some reason? Here is a link to what looks like them but no measurements for sure.
    http://www.hardin-marine.com/p-15906...ith-slots.aspx

    When I remount, it was suggested I use a little permatex high heat sealant?
    Lock-tite for the bolts? I will be replacing them with new stainless as two of the four existing have lost some of their threads in the middle.
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    I have a roll bar for a reason.......


  2. #2
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    Looks like its time for some new manifolds or take them off and get them surfaced. Getting pretty thin in spots.

  3. #3
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    I just got some BBC manifolds in the store on Saturday $275 each. Let me know if you want some part numbers.
    www.BigThunderMarine.com

  4. #4
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    Apparently my IB application is a little unique. Indmar produced a compact manifold for straight inboard applications that resulted in a narrower motor package to allow more walk around room. Most BBC manifolds stick out further and are a square 4" which will not clear my IB dog house motorbox. The risers are also usually shorter and a different angle which could be a problem going into my existing exhaust. There is about a 3' section of 4" flex that drops into what appears to be a fiberglass elbow and then runs another 4' to exit out the transom below the water line.
    Cast Iron manifold with square ports 53-1019 and riser 53-1020 are fairly specific. There was also an oval port manifold for lower 330hp 454 motors instead of the square port 390hp. I really dont know if this is a 330 or 390hp motor. I dont know if PCM had a similar set up?
    I have been able to find some aluminum 53-1078 and 53-1077 manifolds and risers that may be compatable.
    http://marineengineparts.com/shopsit...l/page287.html

    With a 20+ yr old engine, I almost hate to keep taking things a part for fear the repair/replace cancer will just keep spreading back further.
    Pulling the exhaust for honing would be in that realm.

    John, is "thin" a problem yet or something in 5 years? I know this was a brackish boat for some time of its life. It was originally sold in NY state and I bought if from a guy in NJ that used it on fresh and brackish water, hence the perko flush. I have had it 7 years now and do clean out rust flakes each fall when I pull the plugs to winterize.
    I believe the motor has been out of the boat at some point since there is a 12 qt oil deep pan dont know what else may have been done.

  5. #5
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  6. #6
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    Would it be an option to have it welded up and then resurfaced? Just thinking out.... type..... so to type.....
    The difference between an average person and a great person is not whether or not they fail, but how they react when they fail. In the worst of times, true men are born.

  7. #7
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    Quote Originally Posted by BDM View Post
    Would it be an option to have it welded up and then resurfaced? Just thinking out.... type..... so to type.....
    umm, no.
    Boater Mechanics Association, we screw, we nut, we bolt!

    boat [boht] noun- A wood (or fiberglass) lined hole in the water into which one flushes money down.

  8. #8
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    A couple of the ports are thin, but with 20 years of use and some in salt, I would think they still have several years of freshwater life left in them.

  9. #9
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    Would a cautiously used flat file and hone stone work to remove enough to improve the surface?
    I have seen them at 220 grit, can I use more coarse? need to finish with finer?

    I could work it an hour or two vs the effort of pulling the manifold and associated hassles.

    I talked to the shop selling Aluminum exhaust. He recomended if I went AL, to replace both the exhaust and riser due to uneven expansion over time. Cited a prior mercuriser case where they had problems with leaks from Iron and Al comobos.
    Wouldnt I still have different materials between the block and manifold that could lead to a similar issue?

  10. #10
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    Quote Originally Posted by baja22 View Post
    umm, no.
    Just wondering.... I remember doing that on some heads at a machine shop back in high school... didn't know if it was right or not... hence the question.
    The difference between an average person and a great person is not whether or not they fail, but how they react when they fail. In the worst of times, true men are born.

  11. #11
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    Quote Originally Posted by bsloop View Post
    Would a cautiously used flat file and hone stone work to remove enough to improve the surface?
    I have seen them at 220 grit, can I use more coarse? need to finish with finer?

    I could work it an hour or two vs the effort of pulling the manifold and associated hassles.

    I talked to the shop selling Aluminum exhaust. He recomended if I went AL, to replace both the exhaust and riser due to uneven expansion over time. Cited a prior mercuriser case where they had problems with leaks from Iron and Al comobos.
    Wouldnt I still have different materials between the block and manifold that could lead to a similar issue?
    I think it'd be very difficult to maintain a completely flat surface without taking the manifolds off and to a machine shop.... even then I'm not sure if it'd work or not...
    The difference between an average person and a great person is not whether or not they fail, but how they react when they fail. In the worst of times, true men are born.

  12. #12
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    More potentially bad findings when I started digging into the exhaust riser.....

    Passages were very blocked with corrosion. I am almsot suprised any water was getting though but it did seem to have flow the last time I had the motor on a hose.
    I pulled significant debris from the riser by working a screwdriver into the ports and back though the exhaust.

    There is still some debris I could probably continue to work out but thought I would make some determinations before spending more time.
    The riser port walls are in better shape than the exhaust manifold but as you can see from the straight on shot, there is perforation of the separating wall between the exhaust and water. The perforation is after the turn down so no water should flow directly back down the exhaust into the engine but does not look good?
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  13. #13
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    Quote Originally Posted by BDM View Post
    I think it'd be very difficult to maintain a completely flat surface without taking the manifolds off and to a machine shop.... even then I'm not sure if it'd work or not...
    Agreed.

    Those risers are in pretty bad shape. Based on the corrosion inside them, I would guess the insides of the manifolds could be the just as bad.
    It's probably a good time to start shopping for some replacements.

  14. #14
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    Ok, looks like we will be going the replacement route.

    Can I get away with just the one side?
    A concern would be with one new free flowing side and the old, clogged side; too much water would take the route of least resistance and there would not be enough presure to force water to the old side resulting in even less flow than when both sides were "evenly" clogged?

  15. #15
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    In terms of fluid dynamics in other situations, your assertion that water would flow more through the new side and not as much through the old is correct. The flowrate would be higher, but the water pressure itself should be the same on both sides. At least that's how it works in other fluid pressurized systems... should be the same in an engine, I would think.

    My .02 (for what it's worth) would be to replace both sides if you can.
    The difference between an average person and a great person is not whether or not they fail, but how they react when they fail. In the worst of times, true men are born.

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