Re: transducer leakin tar like substance
If it's leaking from the seam where it's put together than yes, time to replace it. The stuff you see is the sound conductive fluid. This fluid is used to transmit the sound from the transducer, thru the housing and into the water and back. Without the fluid, it will not work well or not at all. Naval ships use seawater under preassure to do this.
Art