I read the post about that bogus article about how the Marcum sonar put out too much power output and scared the fish compared to the Vexilar. My question is, what does having 400 watts do compared to 4800 watts of power? Also what about 200khz. vs. 455khz. 
Maybe somebody who is more tech savy than I am can explain. Thank you.
Power output is directly related to the sonar’s sensitivity. A higher output will be able to read objects at a deeper level better than a lower output sonar can. However, a simple 400watt output will do just as well as a 4800watt sonar at the average fishing depth of 20′ or so. The high output sonars don’t really start distinguishing themselves, until depths exceed 50-60′ or so.
The KHz you see associated with sonars refer to the frequency they transmit their signals in. These frequencies determine the cone angle. Frequency=Cone Angle.
Lowrance has some good answers here:
and here:
I wouldn’t make a sweeping decision on power and scaring away fish in my sonar choice but I wouldn’t be surprised at all if it mattered some. Those fish have to hear/feel that sonar and I would think the higher the power, the easier it is to hear/feel it.
If I know a spot well enough to fish it without sonar and it holds big fish, I turn my graphs off. Open water only.
The lowrance article states that the sonar can’t be heard by humans or fish. Why than when I turn on vx-1 pro can I hear a very audible clicking noise?
That clicking noise is also heard in the Vexilars unit as well. Not sure if it can be heard by fish though or how far down it can be heard.
Most higher end units can change the cone angle with the flick of a switch or a push of a button. Does that change then frequency the unit is putting out?
The only noise my fl-8 makes is from the flasher spinning around. The transducers on the 2 units are very different. The vexilar transducer is solid like a hockey puck and is completely quiet when running. The Marcum transducer has a soft plastic covering that doesn’t fit real tight and it makes a very loud clicking sound when running. By very loud I mean I can hear it from across my living room
Sounds like your vex ducer is wearing out. 
All I know is the extra power is nice. I’ve never had the gain over 1-2 and I can fish down to as little as 3′ of water.
Ok, I guess I can’t hear it from across the living room but definatly at least a few feet away. I guess it probably doesn’t effect fish too much but it is noisy and I can feel it clicking. Kinda different I guess but it works
Oh I can hear mine from across the room! They are loud! But, just the other day I had no problem catching fish that were a foot or two under the ducer in shallow water.
Ever hear underwater sound of a school of baitfish? Solid clicks just like a ducer.
Kevin you have the same unit right? My zoom doesn’t seem to work unless I have the setting at the 40′ range. Is that normal?
No, its not.
When you go to use the zoom, turn up the gain just slightly so the bottom is very prevalent. Then hit the zoom button. It should go into split screen. Then turn the gain back down so your jig is shown well on both sides.
But, sometimes if I’m in a school of fish I have to turn the gain DOWN so just the bottom shows for it to go into zoom. Otherwise when I push the button the unit is receiving several different marks as “the bottom” and it just beeps and does nothing.
I really think this is a better question answered by a fish biologist. In some quick looking around I, who is not a fish biologist mind you, found that fish “hear” frequencies in the 0 – 1000 Hz range. This is far lower than 200 KHz (20,000 Hz) that both the Marcum and Vexilar transmit at. If a fish can not hear sounds at that frequency then it should not matter how much power is behind the signal. In being a bit more curious I went and looked at the hydrowave because that is meant to send out sounds in the fishing “hearing” range and sure enough it is sending out very very low frequency in the 1 -100 hz range.
In an experiment by Don McCoy, at the University of Kentucky, he found bass to be most susceptible to frequencies in the neighborhood of 100 Hz, rapidly dropping off after 200 Hz. Anything beyond 600 Hz, they were near deaf.
According to Keith A. Jones, PhD in Knowing Bass, some specialized fish (minnows, goldfish, carp, tetras, and catfish) have hearing approaching an upper range of 10kHz.
The lateral line of fish in general has a detection range of 0.1 Hz to 20-80 Hz. Bass, who have exceptionally narrowlateral line canal systems may be closer to 50-100 Hz.
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