Now you can use your stock transducer but you going to have narrower cone. If it was me think I would opt for this one.
Humminbird XTM-9-DI-25-T
If you go to this one a word of caution. When putting the clamps on to hold it to motor, tighten just enough to hold in place. I have see quite a few that are over tightened and breaks the ears off. His one gives you a wider cone angle for moving around slow.