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Deep Drop - Deep scattering Layer

Old 12-12-2020, 01:20 PM
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Default Deep Drop - Deep scattering Layer

I'm seriously thinking of getting another boat. (24 ft, straight shaft inboard) One of the targeted species will be swordfish using the deep drop method off California coast. I think guys are fishing 1,000 ft with the bait over 1,500 depths. Might be more, not sure.

So, what is the recommended unit and transducer plus wattage. Seems you need chirp to find that deep scattering layer. Some of the guys are using Simrad but I'm a Furuno customer. I don't think the boat will have the space to run a large transducer like depicted in the Furuno install videos that were posted in a thread about the new TZT3 displays.

Thanks,

Bill
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Old 12-12-2020, 06:05 PM
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Airmar 265 pocket or TM will get to those depths depending on what Furuno set- up you have or get
Old 12-12-2020, 08:38 PM
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If going with 1 kw..then on a 24' boat you can use a B175M and also a B175L.
Old 12-13-2020, 04:28 AM
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Originally Posted by semperfifishing View Post
If going with 1 kw..then on a 24' boat you can use a B175M and also a B175L.

This. ⬆️⬆️⬆️ And due to the bottom coverage diameter of the B175L that is the one that I would go with.

if you are using the boat for tuna too then look for a transducer that will give you LHW.
Old 12-13-2020, 01:07 PM
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Originally Posted by Gattafish View Post
This. ⬆️⬆️⬆️ And due to the bottom coverage diameter of the B175L that is the one that I would go with.

if you are using the boat for tuna too then look for a transducer that will give you LHW.
I'll use the boat to find tuna and inshore as well. Thanks
Old 12-13-2020, 01:17 PM
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Originally Posted by semperfifishing View Post
If going with 1 kw..then on a 24' boat you can use a B175M and also a B175L.
Gil, So these would be mounted on each side of the keel?
Old 12-13-2020, 02:12 PM
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Yes, you can install port and starboard.....these come come as tilted element flush mounted and are good from 0 thru 24 degrees deadrise.
Use this app to determine the tilt need at the spot of mounting.
And a B175HW is very good for targets in the water column,,such as tuna, salmon etc. down to about 500-600'
The B175M..less sensitve but will read targets deeper.


https://www.gemeco.com/installapp.php
Old 12-14-2020, 07:45 PM
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To see swordfish at 800-1000 ft deep on the drift, do you recommend the B175 M or L for small boat that needs tilted element?
Old 12-16-2020, 02:51 PM
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High frequency acoustic scattering techniques were used to study the zooplankton masses of DSL. Scientific studies have shown that the acoustic signature (Backscattering) of the Deep scattering layer (DSL) is most highlighted by 38 kHz in depth. While during its vertical migration to the surface, the 70 kHz and 120 kHz frequencies are the most suitable for highlighting Deep scattering layer (DSL).
Old 12-17-2020, 03:51 AM
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I recommend the transducer airmar R109LM. 😉
Old 12-17-2020, 07:50 AM
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Originally Posted by Pat_ View Post
To see swordfish at 800-1000 ft deep on the drift, do you recommend the B175 M or L for small boat that needs tilted element?
these shots are with a B175M. It works for swordfish down to around 1000' and a little beyond but they need to be right under you due to the "narrower" cone. but i think a 2k Low frequency would be better since you would have better depth penetration and a wider cone.




Old 12-18-2020, 04:28 PM
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Originally Posted by Pat_ View Post
To see swordfish at 800-1000 ft deep on the drift, do you recommend the B175 M or L for small boat that needs tilted element?
Pat the 175L will be the best for deeper water. Not sure if you will have 2xTZT3 units or not. But if so I would shoot for a tilted element pair. B175L and a B175HW. If budget is an issue I would start with L as it will work for tuna "OK" - But the HW is better. I have a combo unit that has effectively that pair in a single thru hull transducer. Powered by the TZT3 internal sounder and it works great. No problem marking the scatter layer and the HW works great for fish in the column. But only down to around 500ft.

Old 12-19-2020, 07:53 AM
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Great discussion with some good info for an amateur like myself. Why is nobody recommending the B265LM?
Old 12-19-2020, 02:15 PM
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Originally Posted by Denver Dave View Post
Great discussion with some good info for an amateur like myself. Why is nobody recommending the B265LM?
He mentioned he didn’t have the room to mount the one that Furuno had in their video. Not sure if it was a 599 or 265? The 275LHW would be perfect for him if he has the room. The HW for pelagics and L for swords.
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Old 12-20-2020, 06:51 PM
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I'm using a TM265LM (bought from semperfifishing) Gil has great advice (Transom Mount Combined 1kw Low and 1kw Medium Chirp)
For my setup I had to go with the transom mount since I didn't want to core my hull, but I would suggest thru-hull if possible

We sword a lot in South FL 1,500 to 2,000ft
Most of us aren't trying to mark swords rather make sure we don't hang bottom on the hills and valleys in rockier areas
Anything over 1800ft I find the Low Chirp more useful and typically leave it running the whole time out deep
I have the medium for deep dropping closer inshore but have also found it marks Tuna well in the Bahamas

If you aren't targeting anything on about 800ft of bottom then you might want to go with Gil's suggestion of a L and HW in 1kw port an starboard thru-hull
Worst case if you fishing style changes or you aren't happy with the setup you can swap one of the two separate B175 series out opposed to a larger combined (with fairing block) transducer such as the B265
Another friend of mine has a B175L and B175M port and starboard, it's a great setup

As others noted there are 2kw and 3kw versions out there but they are definitely MUCH bigger in size and space than a 1kw setup


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