Have you got access to the hull of your b,oat at the back of the boat under the splash well? If you have try mounting it there . Pick a spot that is clear of any strakes towards the centre of the boat. You might have to get a shoot-thru-hull transducer. I havent had any success with transom type tranducers with any of the boats I've had. The current boat I have will read the bottom to about 20 odd knots but in deeper water like at Deep Tempest probably down to about 15/18 knots. Still not bad.
Duck