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

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.

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.

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?

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.

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.

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

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.

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