Possible to damage DF by running it with the transducer out of the water?

I talked to a guy today who was advised that he may have damaged his depth finder by running the unit with his trolling motor transducer out of the water.
Is this possible?
I have a 798 CI SI connected to a MinnKota with Ipilot Link. To prevent damage be hitting stumps, I have a bracket on the transom which allows me to raise the transducer out of the water when I am motoring around in stump fields. Of course, the underwater features do not work when I do this, but the mapping feature still shows me the lake map, waypoints, etc.
Am I running the risk of damaging the unit by doing this?

You can turn the sonar (transducer) off by pushing the power button then a menu drops down says sonar off or on with the Humminbird, not gonna say impossible but most likely running your transducer out of the water will not harm it. But some transducers do get hotter than others and that could have an effect

The only transducers that I know of that you can't run out of water due to over heating are the Airmar TM150's. There might be some other chirp ducers that are the same way but I haven't heard of them.

Yes plus all the tank mounted shoot-thru AIRMAR transducers like this one:

http://www.airmartechnology.com/2009/products/marine-product.asp?prodid=266&manf=All

So, turning off the sonar like 44 Diesel said is the way to go for me? Thanks guys, your are a great resource.