bamafish,
Welcome to the forum. Some units work fine together with little or no interference, and some don't as you have found out!
Do you have the Noise Filter turned on? There are several different settings: Low, Med, High1, High2, and High3. Try them all with the Lowrance turned on and see it helps any.
Also, try turning the 83khz off (200khz only) on the Humminbird unit and turn the lowrance to 83khz and see if that does anything. That should turn off the 200khz on the lowrance which is probably causing the problem.
Let me know if that helps,
Robert