Simrad Sounder that Reliably Finds Bottom

[JDCAVE]

The depth I'm failing in is <100', usually <50'...

I have seen the depth reading briefly bounce to 10' while not moving in 25' of water (anchored and stern tied). It freaked me out so I walked the perimeter with a lead line to confirm 25'. While it bounced around, I could see the bottom plot in the sounder view of my MFD jump up and back down again. Playing around with gain and other settings had no effect to eliminate the bounce. I had a couple similar experiences while underway in 1,500' of water. The readings jumped up to 10' feet for many minutes before finding bottom or reading nothing (expected in the extreme depths at the time).

I suspect some sort of "mid water scattering layer" is responsible, either fish, or jellyfish. Zooplankton and sometimes intense layer of dead phytoplankton can also be responsible. Sorry, I should have thought about this earlier. Low powered units sometimes have trouble penetrating a dense layer and still seeing bottom. If the unit is on automatic, it is cycling between low frequency and high frequency. The unit detects a shallow layer and switches to the 200 KHz range and sets the range scale on the display to a shallower setting.

We have encountered jellyfish aggregations in Desolation Sound that are so dense that you worry about them clogging raw water intakes. A dense school of juvenile herring may also be encountered in anchorages.

Jim

 

[JDCAVE]

Also, as discussed by PSNEELD....

 

[JDCAVE]

I was unable to edit the above post to add: try fixing the depth setting to a shallower range and associated frequency when entering an anchorage. That might fix your problem.

 

[twistedtree]

I don't think you should be losing depth in say 10-100' of water. This is where your depth sounder should shine. If you are backing down, then yes, you will lose bottom. And somewhere between 600' and 1600', depending on how powerful your sounder is, you will lose bottom because it's too deep. My lower powered (100W), dedicated depth sounder loses the bottom around 800', and the more powerful (600W) fish finder loses it around 1500-1600'. A 1kw or 3kw sounder will hold bottom even deeper.

So if you are losing bottom and you are not backing down, then I think you do have an issue.

 

[koliver]

The sounder that I use on my dinghy loses the bottom frequently.
The #1 cause is likely a thermocline.
The #2 cause is going too fast, and causing turbulence at the part of the deep V in which the transducer is located.
When it occurs, the reading reverts to a few feet, instead of the 100 to 500 that I would expect, given my knowledge of what the bottom really is.
When I need the reading, eg when I am trying to find the spot to set my prawn traps, I simply revert to the trace function and find the bottom, usually exactly where I expect to find it.

 

[Larry M]

Our Lowrance (Simrad) on the fly bridge, where I fish from, likes the deep water but we do loose shallow depths occasionally. It's 250 watts?

 

[Jetstream]

Our Lowrance (Simrad) on the fly bridge, where I fish from, likes the deep water but we do loose shallow depths occasionally. It's 250 watts?

Nice pictures Larry. I don't know what it is but I like seeing interesting pictures on depth sounders. We use to have a HDS5 they are a good little unit. What transducer are you using there's?

Brett

 

[Larry M]

Nice pictures Larry. I don't know what it is but I like seeing interesting pictures on depth sounders. We use to have a HDS5 they are a good little unit. What transducer are you using there's?

Brett

We were fishing canyons of the coast of Costa Rica for bill fish. The transducer is an Airmar B744V traducer.

 

[boomerang]

Furuno USA Community • View topic - Depth Reading Pay close attention to post #2 from this Furuno forum. I realize that the OP has a 2kw transducer & Chaumu has a 650w transducer but the SIMPLE fact is that a low power unit is the way to go if you want consistently good readings in shallow depths.

 

[chaumu]

After further research and conversations, I'm going to install a DS800 as a secondary depth finder:

DST800 D/S/T, Plastic, 235KHz | Simrad Marine Electronics
http://www.airmar.com/uploads/brochures/dst800.pdf

It's low powered so should work more reliably in shallow depths and it's N2K connected so I don't need to add another screen at the helm. My MFD (NSE12) should prefer the DS800 if my BSM-1 depth reading goes away. And it operates on a different frequency so it shouldn't interfere with the signal from my current transducer (i'm told).

I need a redundant depth source regardless of my bsm flakiness so I don't have too much angst about this unless it doesn't work (plus don't like a new hole below the waterline). Troubleshooting an unreproducable problem at the the dock with the current setup wasn't yielding anything so we'll see how cruising season goes with both readings.