Topic: should I get same DI picture from 997c SI and 958c DI?

[fishcall]

The reason I ask is because I used to own a 997c SI and got excellent down images. I got a new boat that i thought I would sell quickly and never did so I installed a 958c DI to save a few bucks. Well, I'm not getting nearly as good an image that I got in the same areas using my now sold 997c SI. I was wondering if I didn't have the settings right, but then I reviewed the specs of the two units again and discovered that the 997c SI is a 1000watt RMS machine and the 958c DI is a 500watt RMS machine. Is this why I am not seeing  nearly as good down image than I did with the 997c SI machine? I know that the transducer's are different and I installed the 958c DI transducer to shoot-thru hull and my transducer on my 997c SI was mounted on transom. I'm trying to figure out if the the difference that I am seeing is from different installations or different wattage RMS. Do I need to replace the unit with 998c SI or add transom mount transducer to 958c DI? Thank you.

[Humminbird_Greg]

Welcome to the Humminbird Side Imaging Forums fishcall.

What you are asking for we may not be able to provide due to several reasons.

To begin with; I would expect different images from the Di sonar of the 997c Si unit and the DI sonar of the 958c DI unit as these use two different forms of Down Imaging sonar.  The 997 unit uses the sonar data from the two Si sonar elements within its transducer and combines them to display a Di sonar image.  Depending on the menu settings of the 997 unit the Di sonar image could be showing data from a narrower or wider area than that of the 958c DI unit.  The 958c DI unit uses a transducer that has only one element within it to produce the DI sonar image. Most agree that it produces a clearer image versus the Si/Di sonar images of the 997 and other Si model units.

The transducer installation could be affecting the DI sonar image of the 958c DI unit.  If the transducer was not properly installed you could be losing some of the power of the transmitted and received sonar signal as it passes through the boat’s hull.  This could be due to the material of the boat’s hull or the epoxy that was used to mount it with.  Air bubbles/voids in either material can cause this.

The 1,000 watts RMS for the 997c Si unit was due to its ability to use a 50kHz transducer and has nothing to do with the Si/Di sonar.  Though the transmitters and receivers of both units are different which can have an effect on what their sonar will show.

So there are several variables here that can all contribute to the differences that you have seen.  I don’t know which, if any, are the ones that are causing this.

[fishcall]

Thanks Greg, I think that I'll buy a second transducer for my 958c DI and mount to transom first. Do you recommend buying the standard transducer that originally came with the unit or is there a better one? I fish less than 100' in saltwater off of Charleston, SC.

[Humminbird_Greg]

fishcall,
The only optional transducer for the DI model units was designed for the trolling motor.  You would have to rig up your own mounting adapter for it to be mounted there.  So for most folks I would say just go with the standard XNT-9-DI-T transducer.

[fishcall]

Greg, can I use both transducers for same 958c DI unit? One would shoot-thru hull and one mounted on transom. Is there an advantage to this? Do I need a splitter or how does it work? Thanks

[Humminbird_Greg]

You could fishcall but I’m not sure how you think that it would benefit you.
I would expect that you would want to use a TS3 Transducer Switch so that you can change back and forth between transducers, what were you thinking here?

[fishcall]

I had both shoot-thru and transom mount with my old 997c SI. I think the shoot-thru was used for regular sonar and the transom mount for SI/DI. Could I have had unit set-up to do that? I run over lots of shallow water and I kept losing bottom at speed when using just the transom mount SI transducer so I bought the shoot-thru and TS3 switch. Now I have a different boat with a 958c DI and only shoot-thru transducer. I ordered another to transom mount and will report back. thanks for the advice.
Capt. J.R. Waits
Fish Call Charters

[rnvinc]

I had both shoot-thru and transom mount with my old 997c SI. I think the shoot-thru was used for regular sonar and the transom mount for SI/DI. Could I have had unit set-up to do that? I run over lots of shallow water and I kept losing bottom at speed when using just the transom mount SI transducer so I bought the shoot-thru and TS3 switch. Now I have a different boat with a 958c DI and only shoot-thru transducer. I ordered another to transom mount and will report back. thanks for the advice.
Capt. J.R. Waits
Fish Call Charters

This setup (with your old 997 SI) with the TS3 switch does work for using the shoot thru OR the HDSI on the transom...

Some opt to use the AS SIDB Y cable (instead of the TS3 switch)...which disconnects the 2d piezo in the HDSI ...and then all 2d readings come from the shoot thru 2d xducer...

Your new setup with the 958 DI shoot thru and an additional transom mount XNT 9 DI T can be used with either the HB TS3 switch or the AS SIDB Y cable...

This 958 DI setup with the HB TS3 switch would allow 2d/DI to come from the shoot thru DI xducer OR the transom mount XNT 9 DI T ....(dependent on the HB TS3 switch position selection)...

This 958 DI setup with the AS SIDB Y cable would allow DI to come from the transom mount XNT 9 DI T and the 2d to come from the shoot thru DI xducer...(the DI piezo in the shoot thru would not be connected)....

Rickie

[Humminbird_Greg]

But, unlike the old 997 unit, the 958c DI unit normally uses the DI sonar beams for its water depth readings, so the external transom mount DI transducer will still be getting used for water depth readings which sort of defeats the purpose of the shoot-thru transducer.  You can set the 958c DI unit to use the 2D sonar of the shoot-thru transducer but you will have to manually set the “Digital Depth Source” menu for this.

[fishcall]

thanks guys. I will try the transom mount and hopefully get better bottom images.