Transducer position

I may be making too much of this but here goes. I have read that the main reason you do not see fish arches is that the transducer is not pointing straight down.

I have my transducer mounted on the foot of the trolling motor and am wondering if it is actually looking straight down. It seems to me that if the trolling motor shaft is not exactly perpendicular to the bow of the boat, and the boat would have to be perfectly level with the water it will be off. Also, My weight, 225 Lbs, it seems would also affect the angle of the trolling motor shaft.

I may be making too much of this, but any thoughts would be appreciated.

I have often wondered the same thing, on this site it has some helpful information on how they work.
http://www.fishfinder-store.com/howfifiwo.html
I dont know what to tell you on this, other than try to find some sort of counter weight for the back of the boat. or maybe shim the back side of the transducer.

You're transducer can be a few degrees off from pointing straight down and you'll still get arches (under the right conditions) but the front or back of the arch will be longer depending on which way it is angled.

In order to get fish arches like the manufacturers lead us to believe we should, a fish must pass completely through the view or "Cone" of the transducer at just the right speed either because the fish swims through the view or the view passes over the fish. If the fish stays in the view for as long as it takes for the image to move across the screen all your going to see is a solid line across your screen that will continue to show as long as the fish stays in the view. If the fish moves up or down in the water column while staying in the view the line will move up and down accordingly.

On the other hand if a fish swims very fast through the view or the boat (and view) pass over the fish too quickly all you’re going to see on your screen is a small blob or a dot.

Also, if the fish only passes through the edge of the view, even at the proper speed you’re not going to get much of an arch.

So, if your still fishing or “hovering” as we call it when we’re working a brushpile while slowly moving over and around it with minnows and/or jigs, look for solid lines, usually darker than the brushpile. If the lines are moving up and down the fish are active and moving about. If the lines are straight and stay on the screen until you move the boat off of that area then the fish are not very active.

I often see fish (lines) moving deeper as the boat (view) starts to pass over a brushpile and then move back up as the boat stops moving towards the brushpile or backs away some. I’ve also looked down at the graph after a hooked fish ran under the boat and then come off the hook on the way up to see a line come up to a point and go right back down again.

A couple weeks ago when one of my clients was fighting a 16-pound gar (on crappie tackle) it got under the boat and fooled my graph into showing it as the bottom with a depth reading of 6-feet for a few seconds when we were in over 20-feet of water until the fish move out of the view of the graph.

If you want to see what a fish looks like on your graph let a small hooked crappie swim around at different depths in the view of your transducer and see what it looks like on your graph. If you’re not getting a return you need to turn your sensitivity up. You may also need to run your graph in manual mode although on my HB Matrix 12 I can run it with the “Fish ID” on (set at lower sensitivity) and get both lines and an occasional fish symbol showing the depth of the target.

Remember too that the view of the transducer is a cone shape and is much wider towards the bottom than shallower so it will take a deep fish a lot longer to pass through the view than a shallow fish if they are traveling at the same speed.

So, don’t get too hung up on fish arches, especially if you’re Still Fishing or Hovering. And don't worry if your transducer isn't pointed exactly straight down all the time. Learn to read the lines moving across your screen and you’ll have a lot more knowledge about what is or isn’t under your boat.

According to the people at Lowrance you also have to be going at least 3 mph to see an (as advertised) arch. The slower you are going, the more elongated it will be.

[..........So, don’t get too hung up on fish arches, especially if you’re Still Fishing or Hovering. Learn to read the lines moving across your screen and you’ll have a lot more knowledge about what is or isn’t under your boat.[/QUOTE]

Wow, my brother I'm impressed and learned from reading it even though I do it every day. Bottomline is you should learn to read your graph/sonar and let it tell you what it is telling you relative to what you are doing with the boat. Learn to use your graph ( and gps ) and you'll catch more crappie in the long haul. Depth control is key...