Your transducer will look something like a 10 resistive part (actually delivering power to the water) and a say, 200 ohms of capacitive reactance that needs to be tuned out by a series inductor. So you have to measure the voltage across the transducer and alter the frequency and series inductor to get the peak voltage when you have done this, you are in business!!. Because your generator is tooooo big, I would put a series resistor of 100 ohms in series, this will not alter the resonant frequency, so the tuning stays the same but will limit the current to the transducer and save its life.
Frank