I've always heard that the sound of your motor idling will spook fish, as well as the pinging or frequencies from your sonar. However, we've all seen plenty of screenshots of screens full of fish. I'm not sure about the sonar scaring fish but, I've had guys swear that you need to turn it off if you're not trolling or idling around. I think it's obvious that engine idle can depending on the depth of the fish in the water, but what about when fish are down deep? I know for a fact that you can thump fish to the boat. Seen it first hand too many times. So not all sound is bad right? So how much effect does different sounds have on the fish? What got me thinking more heavily about this is something that I'm sure we can all relate to. Some days it is easy to drive around and mark fish, but some days it's like there isn't any fish in the lake at all. What do you guys think?

Interesting theory. As you noted, thumpers certainly work, but motor noise and sonar? Hum...depending on the motor, a 4 stroke certainly makes a lot less noise than a 2 stroke. I should do a comparison next time, if I think of it.
Tim

Barometric pressure being a constant variable, fish become " boat spooked" due to a number of variables . Engine vibration from big motor for sure, some of our gurus will chime in and dispel or underscore. Prolly spending too much brain power over an issue that is simply fishing !!
Will be interesting to hear what Michael Littlejohn shares with regard to this postulate.

I've found constant noise won't spook them ie thumping, engine idling etc... Sudden loud noises like slamming coolers lids, rod boxes, dropping something with weight on the floor etc... will blow them out from under you.

This^^^^^

I never turn my sonar off and constantly catch fish so I certainly don’t think sonar scares them. I’ve never left my motor running so can’t speak to that. I constantly use my trolling motor and thumper and that doesn’t spook them as you said. And two years ago I downrigged white bass and hybrids off a shallow hump in 14-18 fow repeatedly using big motor to move so I’m not too sure how hard these fish are to spook.

Striper are way more spookier than Hybrids and whites, especially in clear water. That being said in the summertime if I got fish underneath me and cant get them to go I will have riley do a cannonball off the back. More times than not soon as she hits the water I will rods go off.

Don't think motor noise makes them spookier. If so, how does one explain catching fish while trolling and the lure is behind the boat ? The lure is usually running the same path close to the prop wash and noise from the motor.

Most people troll with the lure 50 ft or more back unless they have downriggers. Then the lure is down 15 or more feet and back 20 plus feet. If fish are shallower than 8 ft almost anything will spook them. Like Brandon said clear water makes it more so. A shadow will spook them at times.
I’ve seen lmb in clear shallow water spook at shadows also. But not as quick as stripers will usually.
Usually a constant noise like a trolling motor or outboard won’t spook them if they are deep.

Oh

One of the best Down Rigger fisherman on Buchanan swears at 150ft. Now Buchanan usually is somewhat clear down by the dam where the fish are come down rigging season

Running your outboard past a group of guides will spook them for sure. They spend way more time on the water than I do and really don’t appreciate that. In some eastern states people use kicker motors as bubblers (similar to our splashers) to attract fish so motor size may matter.

There are so many different things going on here.

Dense and less dense water allows sounds and vibrations to travel differently through water.

The noise that thumping on the boat makes is not what attracts fish. It’s the vibration off your hull that attracts fish via their lateral line. If you could generate that same vibration silently, the fish would still come.

As far as motor noise and how it relates to fish called in with thumping...nxt time your in open water, watch what happens to the fish stacked under your boat when a boat runs by you 300 yards away.

Those same fish are not nearly as bothered by a boat engine when fish are relating to structure in shallower water, especially when the water is warm.

I used to drift fish the flats between the island and the state park during the winter time, especially icy days. I was younger then and listened to my stereo a lot. I am telling the absolute truth; I would consistently catch more fish playing ZZ-Top or Stevie Ray Vaughn than anything else. Eventually it became a fishing tool when there was a slow day, I'd put the ZZ-Top tape in and boom, the fish were there. Damn near deaf now so I don't listen to the stereo, and don't catch as much fish either. I think those thumper things must have a similar beat as some of the classic rock music.

Very interesting! SRV

Yep as long as the music has a good thumping beat it will call fish in. Bustin Loose song is a fish catcher as well