Transducer for ONLY finding hard bottom Gulf of Mexico

[robarrington]

Snips and others...I've read every thread I can find on this forum regardinging finding hard bottom. I recently purchased a Furuno 588 and a TM260 for the sole purpose of finding hard bottom in the GOM. I have another unit (Simrad EVO) and chirp transducer for finding fish. I've been out on a couple trips and the 260 seems ok at showing tails, but I am wondering if I can improve on that.

Snips, you have recommended the CA50/200 over the 260 for showing tails? If I make that change is it for sure better? Do you have real world experience with the difference? Does the Furuno work better with the CA50/200 since it is a Furuno product?

Also the other option I'm considering is replacing my 260 with the P66. Looking over the data sheets on the airmar website the P66 has a significantly higher Q! Q on the P66 is 21 (50hz) and 36 (200hz). Q on the 260 is between 8 and 10. So if Q is really a big factor for showing tails it seems the P66 should crush the 260. I'd be going from 1kw power to 600W though and I'm not really sure what the implications are for that. I'll only be using this unit in 170' of water and shallower. Does the power affect getting hard bottom tails on the screen?

 

[Johnny Electron]

@Deep Blue is the most likely one to give you the best answer on this. Snips retired and doubtful you will see him on the forum moving forward.

 

[Deep Blue]

robarrington,

When it comes to bottom truthing, you are correct where a typically higher Q transducer is better. Also keep in mind that lower frequencies and having wider beam angles will help expand those bottom tails. So when it comes to bottom truthing, you'll want to select a transducer that has a wider beam width that will provide you a good sampling of the seabed.

The 525STID-PWD 600 watt Transom Mount Transducer (our version of the AIRMAR's P66...) has a beam width of 45° on Low Frequency, and 12° on High Frequency. The TM260 1kW Transom Mount Transducer has a beam width of 19° on it's Low Frequency side, and 6° for it's High Frequency.

For the depth that you intend to fish at 170 ft. or shallower, I would not be afraid to use the 525STID-PWD with that wider Low Frequency beam width. It's going to provide you with a much more seabed bottom coverage than that of the TM260, along with very good bottom tail returns at the depth you want to operate in...

- Deep Blue

 

[robarrington]

Thank you Deep Blue. When I buy the transducer is there any difference between the 525STID-PWD and the P66? Does my Furuno 588 work better with the 525STID-PWD? Or will it be the same?

 

[Johnny Electron]

P66 is the general Airmar model/type number when 525STID-PWD is the more specific part number with the Furuno 10 pin connection on the cable.

 

[jp498]

I'd use manual range+gain, set the range >2x the depth and look for the 2nd echo with a good 50/200 transducer. 600w should be fine in that depth, but much deeper use a 1kw. Or just use a 1kw if you can afford it to overdo it. The 260 should be a good choice.

The attached shows a boulder or something (probably glacial erratic boulder) sitting in mud at about 80 feet. At 160 feet you see a 2nd echo so you know it's a hard object, and no second echo before or after it means mud. The stuff around it at 80'-100' might be the sounder picking it up off-axis (not straight down, before the boat is over the object), or gravel/debris around the object reflecting better than the mud does. Over the right further you see the transition from mud to hard bottom.

 

[jp498]

And if you want a wide view and focused narrow straight down view. Use split 50/200 display, as 50 will be wide and 200 narrow. 50/200 sounders and transducers aren't new tech, but are very refined, understood, and purposeful for studying the bottom.

And the bit about a lower power transducer having a wider view because wider beam angle compared to a bigger powerful transducer isn't quite valid comparison... If two transducers of equal power have different angles for the same freq, then they do. (some Airmar wide variants compared to non-wide variants) Comparing a lower powered one with a higher powered one might be the bigger one has more elements and the way they are aligned means more gain straight down, and the 3 db gain/loss cuttoff for that different shape will mean a different coverage angle by calculation but not in real life.. Same coverage as before, just more gain in the very middle of the pattern because more elements working together.

 

[duemme]

Are there any other tips on how to read the bottom and spot rocks? I've been told that a 50kHz wide beam tends to blend everything together, creating a blind area between two different points in depth (I mean that the shallowest point in the beam is going to be the depth marked on the fishfinder and everything beneath this depth is blended into the red line of the sounder). Do you have any other images? I'm interested in learning how to better read the sounder. Thanks.

 

[robarrington]

Are there any other tips on how to read the bottom and spot rocks? I've been told that a 50kHz wide beam tends to blend everything together, creating a blind area between two different points in depth (I mean that the shallowest point in the beam is going to be the depth marked on the fishfinder and everything beneath this depth is blended into the red line of the sounder). Do you have any other images? I'm interested in learning how to better read the sounder. Thanks.

From everyone I've talked to (and believe me I've read every thread on the internet on this subject and PMd with about 20 different people), 50 is better than 200 at showing hard bottom. But that's hard bottom. If you are just looking for rocks, either should work. That's a little more obvious because it is an object that is sticking up from the bottom. I actually use my sidescan with great results in finding rocks and ledges.