So my tritoon has a sump pump. I’m assuming after reading your comments that it must only service the center toon. I never thought of it before but the toons obviously do not tie together in any way. My S series stays on a dock lift but I have heard a little water noise. I’ve just always kicked on the sump pump and went about my business. Over the water, like it is, it’s hard to tell where the noise is coming from. It sounds like you’ve done all that can be done to diagnose and solve the problem. I do appreciate the conversation. Something to be cognizant of, for sure.