[dgax65]

Wow. And I thought my Lowrance had a big transducer. That must be the 3D transducer.

Too bad; that spot aft of the hatch is ideal. You don't lose any storage space and it doesn't get in the way.

You can mount it on the keel under the center console. It is relatively flat and you will get good performance. The drawback is that it will interfere with stowing rods on the centerline. There is enough room outboard on either side of the hull, so it might not be an issue.

Another option is a wet mount. You construct a small well that you can fill with water (or Vaseline)and place the transducer inside. It might be difficult to construct the well and get a good seal to the hull. You might try plumbers putty on the inside and outside edges when the well is glued down.

Anything off the keel will put the transducer at an angle. This will skew your readings a little.