Where to mount 798 si transducer

[lhumphre]

Here is a pic of the back of my boat, where would you mount 798 si transducer? I am removing the old transducer that is on the pic. Also, should the transducer be below the bottom of the boat or above bottom of boat when mounted? Thanks

[Shellback]

I'd try it just where your old one is mounted. The screw holes may even line up properly because your boat side of the mount looks exactly like my 798si ducer. I think the instructions call for the halfway point of the puck to be even with the left side or lower side as you are looking at it from the stern. That's how I have mine mounted, and it's working well. I had a little interference on the si with the motor trimmed all the way in. But seeing how you normally use your si at slower speeds, I just trim the motor out some, when running the si.

[Humminbird_Greg]

If your old transducer worked well at that location than I agree with what Shellback said.

[lhumphre]

So should my puck be below bottom of boat(current puck is below just a bit? I am nervous I will break puck if I ever run across a shallow stump???? Makes sense to have puck above bottom of boat right?

[Shellback]

If you read the installation instructions for the transducer, it does specify it will be slightly below the bottom of the boat. If you fish stump infested waters, you could try it at the recommended place, then if you have a good picture there, raise it a little at a time till the picture goes bad. Then move it back till the good picture appears again.

[Humminbird_Greg]

Safety versus high-speed depth readings.
This is what you are facing. To get high-speed depth readings the transducer has to be in constant contact with water. Aluminum boats are notorious for having air bubbles flow off the hull making it necessary to install the transducer lower in the water in an attempt to get depth readings at higher boat speeds. This further exposes the transducer to damage from stumps, logs, rocks and other underwater obstructions. This is why a lot of the folks that run fiberglass boats install the Side Imaging (Si) transducers up higher on their transoms (or off the jackplate) and install a second inside-the-hull transducer for high-speed depth readings. You don’t have that option so just be forewarned that you may have to choose between installing the Si transducer in a safer location or installing it for high-speed depth readings. For now though Shellback has given you very good advice.

[lhumphre]

I am running a 25hp 4 stroke yammie, so no speed demon here!! I think i might try it just above the bottom of the boat and see what happens. Thanks!

[Olgrey]

The name escapes me at this moment (Senior Moment), but you might want to consider putting what amounts to a piece of plastic plank on your boat. Lots of places sell them and it enables you to drill a minimum number of holes in your boat hull. You can move your transducer around quite a bit if necessary and just drill holes in the piece of plastic plank keeping you from having to worry about drilling and plugging several holes in your hull. I didn't know about this when I put mine on, but now I wish I had.

[yankee doodler]

Note the mounting bracket that I have custom made. It addresses the issues that Gregg and Shellback talked about as far as high speed issues and stump infested waters. I have been looking at some 1/4 turn knobs to replace the SHCS currently used to tighten down the clamps, but either way I can change the depth fairly easily on the water. Run it deep when on plane, and move it up if moving into dangerous water. Anyway, it's my answer to those issues at this point. Hope it helps.