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B75M plus Evo2s struggling in deeper water

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B75M plus Evo2s struggling in deeper water

Old 06-29-2020, 11:34 AM
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Default B75M plus Evo2s struggling in deeper water

I have a B75M along with SS3D SIMRAD setup on a 23' center console. They have been updated to the latest software. I generally fish in <100' of water. Recently, I have started peaking out into deeper water 150'-250'. I have noticed that my B75M is having some trouble tracking bottom using med chirp when drifting in water deeper than 150'. I don't have a screenshot handy, but it seems to have bottom, but it isn't reporting depth. Oddly, my SS3D downscan is pretty easily tracking bottom at these depths. I haven't really changed settings much on the B75M, so I'm wondering if it's a setting issue. I have only ever updated software as well, so I'm not sure if a factory reset is worth considering. Here's a screenshot of what things looks like in a 100' or so of water. You can see the basic settings I am using at least from it (this was just before latest update). I would assume the B75 should have enough power to operate effectively in 150'+ of water using chirp? Should I be running a fixed frequency instead? I am also including a SS3d shots in deeper water.

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Old 06-29-2020, 02:13 PM
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Is the transducer recognized? If you can select custom frequencies it's recognized.
Old 06-29-2020, 05:55 PM
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Originally Posted by abbor View Post
Is the transducer recognized? If you can select custom frequencies it's recognized.
Yes it is recognized in the sonar menu
Old 06-30-2020, 05:58 PM
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I find this strange, I had expected much better performance from this transducer. But B75M is the only 600W and 1kW Airmar CHIRP transducer element I've not used.
Old 06-30-2020, 06:16 PM
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I would think it would perform better also. Maybe a reset makes sense?
Old 06-30-2020, 08:17 PM
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Try to switch it off chirp and use the fixed 130khz frequency and see how it behaves

I have a B75M connected to a Garmin 1040xs - and im not overly impressed with its performance in water over 150'

Mine marks bottom very well when I set it to 130
Old 06-30-2020, 08:28 PM
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Originally Posted by mrobertson View Post
Try to switch it off chirp and use the fixed 130khz frequency and see how it behaves

I have a B75M connected to a Garmin 1040xs - and im not overly impressed with its performance in water over 150'

Mine marks bottom very well when I set it to 130
Thanks for the tip. I will give it a try and report back.
Old 07-01-2020, 05:50 AM
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I'm thinking about going to a B175M in the off season. The 75 is great in shallow water and mine does OK detecting bottom deeper if I run it at 130 khz ..........but like you I expected a little more from the 75
Old 07-01-2020, 07:11 AM
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Originally Posted by mrobertson View Post
I'm thinking about going to a B175M in the off season. The 75 is great in shallow water and mine does OK detecting bottom deeper if I run it at 130 khz ..........but like you I expected a little more from the 75
I'm having similar thoughts, but I hate to drop another $1000 not to mention enlarging the hole for the b175 won't be fun...
Old 07-01-2020, 07:20 AM
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I think it would be a good idea to get your transducer tested by an Airmar certified installer using TDT-1000. It should give much better performance than what you get.

But there is of course a possibility that your problem is related to noise in the power distribution causing the sonar to automatically decreasing some internal gain settings.
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Old 07-01-2020, 07:41 AM
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Abbor - how would I test an issue on the power side of things? I can contact a local installer about having the B75M tested...
Old 07-01-2020, 09:21 AM
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Set the Gain to manual and increase the gain until you see quite a lot of noise. Post a few screen shots with different, but too high, gain here.
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Old 07-06-2020, 07:54 AM
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@abbor Here's a few screenshots at different gain:
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Old 07-06-2020, 11:38 AM
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Looks quite normal at 84% gain. There are no noise patterns in the two plots with higher gain, doesn't seem to be any electrical or acoustic noise problems. It's just random noise.
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Old 07-06-2020, 03:51 PM
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OP - did your unit do any better by setting and leaving it on 130 khz ?
Old 07-06-2020, 04:03 PM
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Originally Posted by mrobertson View Post
OP - did your unit do any better by setting and leaving it on 130 khz ?
Last time out I stayed shallow. Hopefully in the next week I'll test at 135. I'll report back

Last edited by sbeausol; 07-06-2020 at 07:59 PM.
Old 07-06-2020, 07:31 PM
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Originally Posted by sbeausol View Post
Last time out I stayed shallow. Hopefully in the next week I'll at 135. I'll report back

Sounds good, thanks. Perhaps i have a problem i don't know that i have. My B75M just seems "OK" to me whether on stock settings or manual. Yes, it's "better" when i play with settings but no jaw droppingly better. I feel like I get a better all around picture/performance from mine if i set it to 130 and forget it.

When mine is in chirp - i get alot of screen noise that is hard for me to clean up unless i drop the gain way down...................set it to 130 and screen is crystal clear

Old 07-06-2020, 07:58 PM
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Originally Posted by mrobertson View Post
Sounds good, thanks. Perhaps i have a problem i don't know that i have. My B75M just seems "OK" to me whether on stock settings or manual. Yes, it's "better" when i play with settings but no jaw droppingly better. I feel like I get a better all around picture/performance from mine if i set it to 130 and forget it.

When mine is in chirp - i get alot of screen noise that is hard for me to clean up unless i drop the gain way down...................set it to 130 and screen is crystal clear
I've spoken to a few reputable people offline and their advice has been that the b75 should be performing better. Since I have 2 mfds, one suggestion is to connect to the other one and see if performance changes. Maybe it's the sonar module. I will try that and I will see how fixed freq at 130 performs. After that I will have the local shop test the unit to see if it's faulty. I'm working hard to not buy the B175!
Old 07-09-2020, 05:51 AM
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Originally Posted by sbeausol View Post
I've spoken to a few reputable people offline and their advice has been that the b75 should be performing better. Since I have 2 mfds, one suggestion is to connect to the other one and see if performance changes. Maybe it's the sonar module. I will try that and I will see how fixed freq at 130 performs. After that I will have the local shop test the unit to see if it's faulty. I'm working hard to not buy the B175!
I was able to test more yesterday. I have 2 evo2s so I switched the transducer input to my other evo2 and took the boat out. I immediately noticed an improvement on the B75M. I was able to hold bottom much better on plane and
​fish marks seemed to be much more robust. At first glance, it seems the sonar module on the original evo2 I was plugged in to isn't putting out as much power. Is this something that can be remedied or repaired easily? It was too rough to move out to deeper water but the improvements in <100' were noticable switching to the other evo2. If I can confirm in deeper water I think this rules out b75m as the issue and points to the sonar module on the evo2. Has anyone else had this happen?
Old 07-09-2020, 11:12 AM
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There may be an estimated capacitor problem.

For the evo 2, which you think is a loss of power, check the power cables. Is there oxide and relaxation.



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