I recently bought a used LCX 15 and mounted the transducer on my trolling motor. When I turned it on I can hear the tranducer pulsing. The pulse pattern is fast then slow and alternates this pattern constantly. Is this OK? I thought is should be a constant interval for the sound of the pulse. has anyone else experienced this with the transducer out of the water?

Yes.  I have the same setup and you can hear it.  Mine is pretty steady, however.  But it's not perfect intervals.  It has a beat, but you can't dance to it.