I dont think it would hurt the unit (maybe the ducer). Now I only run 50khz when over 80 FOW. I can see my rigger balls no prob. 200khz not really. I was out there and there was some wicked currents going on. I run 13lb balls and was loosing them on my screen at 2.6 mph at the ball.
You are using 10's so your balls are out of the transducer area and thats why you cant see them.
200khz is for shallow applications, 50khz for deep water. Sometimes I run a split screen 50/200 to make sure I'm not missing fish up high, but just try the 50 when over 80 fow. You will mark more fish too. you definately need bigger balls too!
good luck
RR