The factory installed thru-hull Lawrence depth finder in my recently purchased 1994 200 Overnighter spends 60% of the time blank when on the water. I've been told the next time it's out of the water to make sure the transceiver hasn't been painted over with bottom paint. I've also been told, unknown reliability, that the older transceivers had a narrower perspective so it may be transmitting and "missing" the bounce back off the lake bottom.
