I have a Hummingbird Smartcast RF15, I recently purchased a replacement transducer (rf45). I tested it in the sink and it seemed to work fine, or as well as it would in a sink, but the temp did not show up as it advertised it would. Upon getting to the lake it did not work properly, the light was very dim, the screen shows alot of clutter. Reading the manual it says that the problem i am having can be caused by using two channels at once. I am wondering if it is due to low batteries and will put new batteries in it and try again, the only thing is that it works fine at home in the sink. Does anyone have one of these units and if so have you ever had this problem? Btw it worked fine with the old transducer, but it is lost somewhere...