all transducers can shoot thru hull ( ONLY in a FIBERGLASS BOAT ) , there are advantages and disadvantages with both ways, biggest advantage to shoot thru hull is high speed, if your boat is fast enuff it will rise up out of the water, and only a small portion of your hull pad will be in water .. and your transducer is out of the water at that point if mounted to the outside of your transom.
Also prop wash will mess up signal, and give you false readings. not to mention your putting holes in your transom and allowing water another way to enter the wood in your transom, unless you are lucky enuff to have one of the newer all composite boats that have no wood.
Mounted inside shooting tru hull takes care of those 3 probs.. and you may loose a slight amount of signal , but the benefits in my opinion out way the the slight possible signal loss.
The biggest prob with mounting to shoot thru hull .. finding a place in your boat on the rear pad that is accessible and is thin enuff to read thru hull. You will need to mount by setting the transducer in a bed of epoxy and that epoxy has to be bubble free, or make a water box to sit you transducer in here a link on how to make a water box and other solutions for thru hull mounting
http://www.tritonclass.org/mir/TRANSDUCERS.htm
I would at least use a water box to find a location in your boat to mount the transducer before epoxy to hull.
I only used mine to find structure and depth while underway.. while fishing mine is mounted to trolling motor on a separate LCR