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Underwater Exhaust-- good, bad or indifferent to raising fish?

Discussion in 'Technical Discussion' started by Fortunate One, Feb 17, 2007.

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  1. Fortunate One

    Fortunate One New Member

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    I'm wondering if exiting the exhaust under the boat would have any negative effect on catching fish.

    I'm in the process of having a wooden/epoxy boat built and I'd like to go with an underwater exhaust.

    That is unless I hear that it's not the way to go.

    So my question is should I consider going with an underwater exhaust system on a sport fishing boat?

    Any real life experience would be appreciated.

    Michael
  2. cranky

    cranky New Member

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    Can't say I am an expert on this but several years ago I got into this discussion with an older guy who had several about "60 or so" I believe world records over the years. his belief was the quieter and less turbulant that the vessel was the better.
  3. Loren Schweizer

    Loren Schweizer YF Associate Writer

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    I'm with cranky.
    There once was a 42 sportfisherman built by a renowned manufacturer. All the other 42s ever built caught fish except this one.
    The mystery was solved when an astute mechanic found that one of the prop shafts was so poorly aligned with the shaft log, it left bronze "sawdust" in the bilge from the wear and scraping between the two-- must have made some kind of racket underwater.

    With proper clearance between the two-- and, presumably, no more noise-- the boat entered a tournament and caught fish.

    I was a firsthand witness to all this, BTW.
  4. Fortunate One

    Fortunate One New Member

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    So are you guys saying that they are not good?
  5. Loren Schweizer

    Loren Schweizer YF Associate Writer

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    Fortunate One:

    I cannot imagine introducing noise into a relatively noiseless environment as a fish-attracter.
    Would your underwater exhaust have an above WL relief outlet for low rpms when the backpressure is high relative to what's coming off the turbo which would render the issue moot?
  6. CaptainSilva

    CaptainSilva Senior Member

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    I'd have to agree that underwater exhaust wouldn't be the most practical installation on a fishing boat. With the exception of deep-water bottom fishing (80+ feet) for things like cod, introducing turbulance and sound into a relatively calm environment isn't the best idea.
  7. Codger

    Codger YF Wisdom Dept.

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    From the point of view of the fish

    Used to do some diving. The fish would definately react to those boats going past overhead with underwater exhausts. I can't positively state that the reactions were to the noise 30 feet overhead or recognition that the driver of the boat was probably just a general danger since there were half a dozen diving buoys/flags up there that he had missed.
  8. nas130

    nas130 Member

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    Why do some engines raise more fish? Who is to say that loud noise scares fish, I am sure there are many people on here who have caught many fish doing a crossing with underwater exhaust. I am playing devils advocate here because I do not fish that much, but the engine point has been said by many knowledgeable fisherman.

    A full underwater exhaust is quieter on board, how much are you going to be fishing vs cruising?

    nas
  9. CaptainSilva

    CaptainSilva Senior Member

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    It's not the engine that raises/scares more fish. It has to do with exhaust location, and hull design. The less turbulant the wake is behind the boat while trolling the better for nearly every type of fishing you're doing. If the exhaust is exiting in the water below the boat you're not only adding sound, you're adding air and turbulant water to the environment as well. You want your baits to look as natural as possible, and need the fish to see them as well. Turbulant water will prevent that.
  10. brian eiland

    brian eiland Senior Member

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    I wrote a similar thing on my website discussing 'fishing under sail';
    "I've also heard the many claims by various captains about their individual boat's particular sound being an attraction for raising fish. I find it difficult to believe that a very loud (water is a great amplifier and transmitter of sound), foreign sound would act to attract a large predator fish seeking out their food source in the ocean's natural environment. Loud, unnatural noises have in most cases acted to disperse aquatic life."

    I 'borrowed' a few of you guy's comments and placed them here:
    http://www.yachtforums.com/forums/39126-post38.html in my Gamefishing Under Sail forum topic