Maybe give this a thought. NO Depth Sounder at all. In a boat doing say 30 MPH, by the time the "signal" from the transducer gets to the guage on the dash..which is very fast...AND you just happen to be looking at the guage at that
same instant..You have ALREADY passed over that rock and whacked your outdrive. YUP
I am the same way, when it comes to drilling holes in the hull..
Particularly below the waterline. Just don't like to do it....even though the factory does it all the time.
As stated in a couple of posts above, NOTHING will adhere to that cutting board material for very long, if at all...except maybe silicone seal. (RTV) In fact, I'm going to take a guess that the cutting board material might just be
Nylon or even
Teflon. No Stick. NB
EDIT: How about substituting a block of 1/2 inch plywood (marine ply if possible) for the cutting board.. thouroughly sealed and painted on all sides and edges..THEN stuck on the transom with RTV.
EDIT. Epoxy is TOO Permanent.