My boat came with a flasher unit and a crapped out transducer. I got a used transducer from a friend in the marine electronics business, wired it to the display and carefully munged it place to the inside of the hull next to the existing transducer using some decent quality silicon caulk. It won't work if there are any air pockets in the caulking or your glass laminate. Mine worked fine but it had trouble reading depths over 100' after shooting through 3/4" of fiberglass.