Ducer Losing Depth When Shallow

[UaVaj]

The ducer is a 20 degree thru hull airmar B60 600w ducer installed on a 25 degree hull. Once I get to anything less than 6' - it loses bottom.

Question for the experts - what is happening to the signal for me to lose bottom when it becomes shallow.

[dssmith]

Originally Posted by UaVaj

The ducer is a 20 degree thru hull airmar B60 600w ducer installed on a 25 degree hull. Once I get to anything less than 6' - it loses bottom.

Question for the experts - what is happening to the signal for me to lose bottom when it becomes shallow.

I'm no expert. I have Humminbird's that do the same thing. Useless in less than 5' of water. The units do tell me speed and temp, but in less than 5.5' I get a blinking response from the digital readouts indicating the unit doesn't make sense of it's readings. Once I get deeper the units seem to work fine.

I have a Matrix 37 on my offshore boat and a brand new 343c on my inshore boat.

For what it's worth, the Humminbird guy suggested I put it on the fresh water setting (instead of the salt water setting) and reduce the sensitivity some when in shallower water.

This makes some sense. My units appear to be sending out so much power that the unit has trouble making sense of such a strong response received in shallow water. You might also try adjusting the surface clutter setting and see if this gets you some reliable readings in less than 5' of water. The cone of your bottom reading from your sounder in less than 6' of water is a patch probably a couple feet across, so shallow water fishing finding is pretty much useless. It is helpful to know your depth, especially if you are in rocky or hard bottom areas. I'm mostly in mud and flats, but do wish my units were reliable down to a couple feet or so.

[LI32]

It is not the ducer, it is the fishfinder - too much power for the depth, reduce the gain as much as you can and keep it on 200kHz.
I have a B60 with a Garmin GSD 22 on my small boat, and it is good to about 2.2'
On my bigger boat I have one of those Airmar 235 kHz NMEA 2000 triducer, and it is good to 1.7' and maybe less (as shallow as I've tested it - don't really like to beach the boat).
My Furuno FCV-585 and B164 is good to about 2.7' before it becomes erratic while my Garmin GSD 22 and M260 is good to 2.1' on the same boat, with the transducer in the same location, opposite side of the keel. So that is why it is my opinion it is the fishfinder that is a bigger factor

[C Skip R]

Interesting I have a Furuno FCV1100 with a R199 2kw transducer and it picks up the depth to zero with the 50 and 200.

[UaVaj]

Originally Posted by skiphughes

Interesting I have a Furuno FCV1100 with a R199 2kw transducer and it picks up the depth to zero with the 50 and 200.

When you say zero.

Do you mean - you do beach your boat - so you can actually see the depth track down to zero. At zero (in actuality about 1') the keel of the bow should be on sand. That would be the only way to verfy.

If that assumption is incorrect. Please do tell how you go about zero-ing out the sounder.

[UaVaj]

My original thoughts were that. It has to do with the angle of attack (poor instalation). So unless the angle of attack is straight down. Once it gets too shallow - the cone angle become so narrow and if that cone angle isn't straight down. The return signal bounces back beyond/outside the cone's angle/shape (reading area) causing the ducer to get a no reading / error reading.

[TripleCrownNC]

This is straight from Furuno tech support:

Sound(er) Advice
Here are a few adjustments to help maintain a consistently accurate digital depth indication:
--- If you are in 100’ or less, I suggest using the high frequency (200khz).
---Try using the MANUAL mode instead of cruising or fishing modes.
---Then temporarily set your RANGE so you can see 2 or 3 times your present estimated depth.
---Then adjust the GAIN so you can see your bottom echo and just a slight, faint second bottom echo at twice the depth. If you see a third echo at 3 times the depth, then you have too much gain.
---Once you have your real bottom echo and a faint trace of the second echo, you can then adjust the RANGE down so you can see zero to whatever depth is appropriate for the area you are in.

These simple steps should help increase your ability to have consistent, accurate digital depth indications in the lower-left corner of the display screen.

[spearnreel]

Originally Posted by TripleCrownNC

This is straight from Furuno tech support:
---Try using the MANUAL mode instead of cruising or fishing modes.

Bingo! Auto functions are your worst enemies.

[UaVaj]

Originally Posted by spearnreel

Bingo! Auto functions are your worst enemies.

How about smart auto functions. Kinda like you tune it / learn it. Then when the depth get to a certain depth the gain setting automactically adjust.

Isn't that what superHD sounder is?