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46' Post SF Sinks

Discussion in 'Post Yacht' started by Jimbo1959, Sep 1, 2014.

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  1. NEO56

    NEO56 Member

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    HELLO!!!! Black Cloud indeed....why didn't he just name the boat "Please Sink On Me" or "Lucky No. 13" or "Unsinkable Molly"...I know there's more, Oh yeah "Davey Jones Locker" C'mon guys help me out here.

    O.K. I feel bad for the guy, but better to sink at the dock than 20 miles offshore. I'd be willing to bet when his insurance agent hands over a check the conversation goes something like this, "Jim, I'm really sorry that this happened, but once you get her fixed up, you might want to re-think the name."
  2. Jimbo1959

    Jimbo1959 Member

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    Pictures of muffler

    Port side muffler.

    Attached Files:

  3. Capt J

    Capt J Senior Member

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    That looks like it's been stress cracked a long time.....almost like it was damaged previously from a poor winterization or something.....
  4. NEO56

    NEO56 Member

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    I agree Capt J, that was years in the making, the serrated edges clearly make that case, if it was a back pressure explosion it would have been a much cleaner hole, that is a fatigued piece of pipe.
  5. NYCAP123

    NYCAP123 Senior Member

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    Looking at the pictures, I can't honestly say it was a long-standing problem or not, but the loud bang and "2 minutes" between up and down indicates a catastrophic failure whether there was a fault or not. This is scary stuff, and it seems indefensible against, except at the design stage. We all have plans in the backs of our heads for holes, but they all will take a few minutes to impliment. This indicates the possibility of an achilies heal that could exist on a lot of boats. I'd be curious to hear the opinion of some designers (NAs). In the mean time this indicates the clear need for an EPIRB and to keep your PFDs readily accessible.
  6. Marmot

    Marmot Senior Member

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    Sure looks like a failed seam at the bottom.
  7. 61c40

    61c40 Member

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    Starting fluid ??
  8. Jimbo1959

    Jimbo1959 Member

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    No starting fluid, engine lit right off. Makes me wonder, what is the life of these things? and should you just replace mufflers after so many hours or years? Scary, as someone earlier said. These guys fish extensively offshore, up to a 100 miles out. If it blew out on a fishing trip a 100 miles offshore no one would have any time to get a life raft or jacket on or even make a distress call.
    Jim
  9. Beau

    Beau Senior Member

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    That's some hole! I keep a couple of mustang jackets on the back of my helm chairs just in case I have to go in the water in a hurry. I figure by the time I get them out from under some seat, etc. I'm already floating?
  10. chesapeake46

    chesapeake46 Senior Member

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    Still does not explain the "BANG "

    My Wife and I have our personal life preservers on the bridge with us.
    Not stowed but loose on the seat right with us.
    Attached to each is a plastic whistle and a personal strobe light.
  11. chesapeake46

    chesapeake46 Senior Member

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    Any maintenance work done to the cooling system prior to the big bang ?
  12. NEO56

    NEO56 Member

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    Marmot, Did you get my PM?
  13. Capt J

    Capt J Senior Member

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    My theory is the exhaust was weak noticed by the old stress cracking on the inside of it. Something had floated into the exhaust causing excessive back pressure (dead animal, coconut, etc.). When the engine started there was excessive back pressure, and the bang was the side of the muffler exploding. There was no way a piece like that blew off without creating a bang noise.....sort of like when you fill a plastic bag or ballon with air and then smash it cause it to explode.
  14. Beau

    Beau Senior Member

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    So re-reading the OP, this event occurred shortly after launch and preparing for a sea trial. Wonder when the last start up occurred. {later post says a few days earlier?} Was the boat stored on land or in the water, previously? Not an engineer, but that looks like an inside to outside failure. What else other than back pressure can do that? If it were in the water for a while, you'd think, ok, the engines hadn't been started for a while so something went up the exhaust and clogged it. On the other hand the boat had just been launched a few days earlier or at least started a few days earlier. How did they move it to the slip, if they did? No answers, just questions from here.
  15. Capt Ralph

    Capt Ralph Senior Member

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    Does the gen-set exhaust dump into the same 8" hole in the transom? Gas pump near? With some imagination follow this;
    Unburned fuel from the gen-set back flowed into the muffler. Existing fuel in the muffler. Floating slick from a gas spill next door got up there. Light an old 671 up and some hot gasses, (near flame) comes down the line, igniting by this time some warm fumes.

    Thoughts?
  16. Beau

    Beau Senior Member

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    Tight set of facts, but theoretically possible. Interesting question about the diesel gen exhaust, if thru the same "hole" does that increase the back pressure theory possibility? Hope Jimbo can get us some more info....
  17. NYCAP123

    NYCAP123 Senior Member

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    "within in seconds they heard a loud bang". Doesn't sound like you'd have hot anything, much less "near flame". Back pressure makes the most sense.
  18. Capt Ralph

    Capt Ralph Senior Member

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    Yep, within seconds is what it would take for the first exhaust flame to come down the exhaust hose. You ever seen a engine lit with no exhaust manifold. Hot carbon flakes, sparks and sometimes flames pop out. Even on diesel.
    Back pressure or explosion. Some kind of gas was expanding.

    First seconds may not have any water from the bump cans either.
  19. Jimbo1959

    Jimbo1959 Member

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    The boat was on the hard for better than 6 months. When she was launched, the engines were started while being held in the slings in case there was an issue. No problems engines started on first turn, water flow was good, no leaks at shaft logs or thru-hulls, she went into the slip under her power. During a 3 day period while she was in the slip, they started and ran the engines numerous times. After gathering the family for sea trial they started the generator. The genny exhaust is plumbed through its own muffler and thru-hull out the port side of the boat. Everybody got on board and the port engine was started, a bang was heard, some smoke, the family scrambled to get off and down she went.

    After looking inside the muffler, It becomes a question how long should they last. BTW there are no signs of any external cracks on whats left or the other side muffler.
    Jim
  20. Jimbo1959

    Jimbo1959 Member

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    Rcrapps, Remember this is a turbo charged engine. By the time the exhaust exits the turbo flames would be gone, especially during idle, I agree with you that you can get sparks, but they would usually occur during a hard throttle event. Just idling nothing.
    Jim

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