Topic: 998c SI questions

[Capt. Shodamane]

Hello everybody, a month or so ago I had posted about buying a 998c unit. I have purchased the unit and have installed everything on my Nitro Z-7, and have to say everything is working 100% so far. I have taken the boat out 4 or 5 times so far since the installation and my first trip out got picture perfect images! I have a few questions though. First, if you are looking from the back of the boat at the transducer, it is perfectly level with the boat. But if you look from the side of the boat, the transducer is tilted downward a few degrees. I haven't noticed any issues reading the bottom, even at high speeds. (45 mph +, with the 2d sonar) However, when marking fish with DI and 2D, the fish don't quite show the traditional "arc" or "^". It's more of a slightly tilted arc. Could it be because of the angle of my transducer? other than that, the images are perfect. The only other problem I have had is the transducer will kick up at WOT. Is it possible to tighten the bracket so It wont kick up? I know it needs to be able to, but I was hoping to prevent it from kicking up at higher speeds. I have the transducer mounted on the step of my nitro if it helps with anything. thanks in advance, and i'm still mind blown at the things I have found in my home lake already...

[SonarTRX]

Hi Shodamane,

Yes, if the transducer is tilted and/or not level, the fish-arc's from 2D might not be symmetric.

The asymmetry is simply because the fish might "enter the beam" at a different range then when it "exits the beam", as the boat passes over the fish.
Had the transducer been perfectly level and with zero tilt, the entry/exit range would be the same (assuming that the fish is at a constant depth and that the "cone of sound" is perfectly symmetric.)


Tore

[Capt. Shodamane]

Can anyone enlighten me on the proper way to tilt the transducer upward a few degrees? also, is it possible to tighten the kick up tension?

[Humminbird_Greg]

For the 998c Si unit that big HDSi transducer can be set to any angle by loosening the screws that hold the transducer itself to the black plastic “pivot arm”.  If you have not re-tightened the transducer yet you may be able to just bump it with your hand to change the angle.  This joint in the transducer has some star type lock washers and they typically set into the plastic after a few uses and sometimes loosen the transducer up a little, so you may need to tighten the screws again after adjusting it.

If the leading edge (left side) of the fish arches are longer, that means the transducer is too low in the backend and needs to be tilted up.  If the training edge (right side) of the fish arches are longer, then the transducer is too high in the backend and needs to be lowered.  Make very small adjustments here if there is only a small amount of difference between the leading and trailing edges of the fish arches.

To increase the hold down force of the bracket: kick the transducer up and bend the “ears” or sides of the metal bracket in towards each other.