Furuno LS4100 Fish Finder



I have a high end color LCD chartplotter on my helm but I will be using this on my tramsom for drift fishing. I'm concerned about a sinker from a three way smashing into the screen while a Fluke thrashes about on the deck. Is there any way I can put a clear plastic cover over just the screen?
There is no clear plastic cover option. The white plastic cover for the unit is only for when it isn't powered on. (to protect the screen)
If you were to covered the unit with it turned on, it might become a heat issue.
Johnny ..... wonder if you can help me. I'm posting on this thread as I'm running an LS-4100 on our Bayliner 3270. I get good bottom echo and display in automatic mode on 200khz. But no digital depth read out on lower left of screen. I've tried all modes (Auto crusing and fishing and manual and also 50khz too) ... and still no depth read out in botton left corner. Any suggestions on what I need to do with my setup? Many thanks