I have two totalscan transducers on different boats that have cracks on the rear of the transducer. 

One is fairly old and the other is 1 year old. 

The oldest one looks like the entire back of the transducer could fall off.  It does have damage but I don't know from what

The newer one has a crack just developing and no damage.

Any idea what would cause this?  I turn off the sonar if the machine is running out of the water.

Both transducers are hooked up to  Lowrance gen 3s

If I can figure out how to post pics i will