How Fast Can You Go And Still Have Clear Screen On Fish Finder?

BoatNoobie

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So I have a Humminbird 798C SI installed on my Lowe. At low speeds, say 5MPH or less, I get a nice clear side imaging picture and regular sonar.

But once I hit 6MPH, I start seeing little dotted vertical lines on the screen in 2D. But for the most part, the screen is a clear and you can read everything just fine.

When I go WOT and going about 30 MPH, my screen is a mess, but I can track bottom. Cant see what is what though, except you know the depth.

Is this "normal"?

*edit* to clarify, at the higher speeds, I'm refering to 2D.

SI is only good up to 6MPH according to the manual.
 

John_S

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Jun 21, 2004
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Re: How Fast Can You Go And Still Have Clear Screen On Fish Finder?

At 30mph I track bottom in 2D. The deepest the lake gets is around 130ft. I do get some hash. Si is not worth much above 15mph, and I prefer 5-6mph. Finding a good transom position that will give good 2D and SI is a challenge. Many resort to a seperate 2D transducer and splitter cable, especially on high speed bass boats.
 

BoatNoobie

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Re: How Fast Can You Go And Still Have Clear Screen On Fish Finder?

At 30mph I track bottom in 2D. The deepest the lake gets is around 130ft. I do get some hash. Si is not worth much above 15mph, and I prefer 5-6mph. Finding a good transom position that will give good 2D and SI is a challenge. Many resort to a seperate 2D transducer and splitter cable, especially on high speed bass boats.

so at 30MPH, you can mark fish clearly in 2D?
 

John_S

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Re: How Fast Can You Go And Still Have Clear Screen On Fish Finder?

so at 30MPH, you can mark fish clearly in 2D?

Not always clearly, but suspended fish like Lake Trout, yes. They are usually down around 60-70' in our lake. I don't fish for them, but if I see a bait ball or school in less thean 30ft, that will get me off plane. I rarely search for fish, I mainly want to find the structure, so for that it is always less than 10mph.
 

BoatNoobie

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Re: How Fast Can You Go And Still Have Clear Screen On Fish Finder?

any other inputs?
 

edrhoades85

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Aug 24, 2010
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Re: How Fast Can You Go And Still Have Clear Screen On Fish Finder?

How fast you can go will dpend on the fishfinder. Also how strong the transducer is, what your gain is set to, and what frequency you are running in. My Garmin will track to 30mph sometimes and othertimes it will not.
 

SteveRoss

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Jun 14, 2010
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Re: How Fast Can You Go And Still Have Clear Screen On Fish Finder?

I have a little Humminbird Piranah Max 160 (I'm sure I misspelled all of that), and it never looses contact with the bottom. I always know how deep the water is. Of course, it's mounted on a little 14 foot Jon with a Honda 15 on the back, so the speed prolly isn't so great..... So what...

If you are going 50 or 60 mph or so and see a stump at a foot deep, it's tooooooooooo late !!

All the best...

Steve LOL
 

dingbat

Supreme Mariner
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Nov 20, 2001
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15,417
Re: How Fast Can You Go And Still Have Clear Screen On Fish Finder?

Good clean picture and good "marks" to WOT@ 35 kts.

Furuno 585 w/Airmar B160 1kW Thru hull transducer
 

BeaufortTJustice

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Oct 8, 2009
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Re: How Fast Can You Go And Still Have Clear Screen On Fish Finder?

Up to WOT (45 - 46 mph) I have clear readings...Garmin 160c with transom mounted transducer.
 

PGFISHER

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Re: How Fast Can You Go And Still Have Clear Screen On Fish Finder?

I have an old lowrence. At 5-6 MPH I see lots of fish; but when I stop, they all dissapear. I'm reading bubbles from my pontoon; however the depth finder is always correct; even to 300-400'.
 

BoatNoobie

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Re: How Fast Can You Go And Still Have Clear Screen On Fish Finder?

so i managed to get some pics off my screen before i winterized the boat. Is this caused by bubbles or interference? The wires are connected directly to the same battery as motor.

The screen is crystal clear at low throttle.
hmb2.jpg



But when I get to a certain position, this starts happening. Gets worse as speed increases. You can hear a change in tone in the engine or whatever. Makes a little squeeling sound. This was at just under 6 MPH.

hmb1.jpg
 

John_S

Rear Admiral
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Re: How Fast Can You Go And Still Have Clear Screen On Fish Finder?

Does the noise show up if you rev the engine in neutral? Clear screen at 4.2mph but fills with noise before 6mph.
 

Fl_Richard

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Re: How Fast Can You Go And Still Have Clear Screen On Fish Finder?

Is the left side of your screen obscured by the hull? My side scan bottom profile is identical on both sides. I can scan the bottom albeit with some noise (horizontal lines) upmto about 30 knots. The image has distortion but you can still see bottom structure detail.

I can scan clearly up to about 8 mph after she comes up on a plane the distortion is evident but bottom is still viewable.

I would try adjusting the transducer angle. It should dig into the water slightly on the trailing edge. I aLso scuffed the bottom of the transducer -I heard it would help - the juries still out.

The number 1 improvement has been through frequently checking for and installing the software upgrades. They have improved the unit 200% since i bought it three years ago.
 

BoatNoobie

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Re: How Fast Can You Go And Still Have Clear Screen On Fish Finder?

Does the noise show up if you rev the engine in neutral? Clear screen at 4.2mph but fills with noise before 6mph.

I've never checked that. Will need to write that down and test next Spring. so I assume, if I get the same reading on screen while in neutral, it means motor interference?



Is the left side of your screen obscured by the hull? My side scan bottom profile is identical on both sides. I can scan the bottom albeit with some noise (horizontal lines) upmto about 30 knots. The image has distortion but you can still see bottom structure detail.

I can scan clearly up to about 8 mph after she comes up on a plane the distortion is evident but bottom is still viewable.

I would try adjusting the transducer angle. It should dig into the water slightly on the trailing edge. I aLso scuffed the bottom of the transducer -I heard it would help - the juries still out.

The number 1 improvement has been through frequently checking for and installing the software upgrades. They have improved the unit 200% since i bought it three years ago.

Yeah, I cant get my left side reading due to my motor. When the trim is all the way down, it blocks the transducer if the water is deeper than ~20ft. Shallower than that, it seems fine. I can trim up the motor to get a left reading whenever I want though.
 

John_S

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Re: How Fast Can You Go And Still Have Clear Screen On Fish Finder?

I've never checked that. Will need to write that down and test next Spring. so I assume, if I get the same reading on screen while in neutral, it means motor interference?


Yes, that could be the problem. Contact HB tech support and send them the pictures. They have some tips and recommendations if it is noise.

Also, take some pictures of your transducer mount. One from the back level w/XD, one from side level w/XD, and one showing the upstream hull.
 

xeddog

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Oct 23, 2009
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Re: How Fast Can You Go And Still Have Clear Screen On Fish Finder?

I have recently added a Humminbird 788ci with the QuadraBeam transom mounted transducer to my boat. I would say that my results are pretty much as you describe, without the side scan of course. Even when I am running at 45 mph I get a good bottom read.

I have to keep the FishID+ on because my wife wants to see the little fish symbols. Even at 30mph I see some of the fish symbols, but I don't trust them since the screen is pretty messed up at that speed. But the fish symbols always seem to be at consistent depths so they could be legit. While at Berryessa a few weeks ago, I would see fish symbols at either 80-90' or 40-50' but not much in between. The bottom was reading around 100-120', and Kokes were hanging around the 40-50 foot mark. I have no idea what was in the 80-90' range if anything.

Wayne
 
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