Simrad nss evo 3 on Boston whaler 250 outrage.

The high wide would be a bad choice for bottom fishing. The wide cone angle allows maximum coverage of the water column under the boat, but because of that you lose definition.  If you are looking to see when you have fish under the boat the wide is great, but if you are looking for seperation on the bottom, or wanting to get right next to a drop-off then the wide will not get you there, you need the narrow for that.  

You will need 20 degree for your whaler.  Make sure you have a solid section of fiberglass in your hull bottom for a thru-hull.  If you don't you'll need to remove foam core and make one. A very time consuming process on a whaler.