Thanks for your replies. I have a Grady-White that has lots of foam in
the hull with one thin area in the stern (as noted by the
manufacturer). Placing a transducer there yields a clear bottom scan
with a thin line at the surface (the hull) that doesn't seem to mess up
the readings to a noticeable degree.

All I really want is some assistance in avoidance of running aground in
the tributaries of Chesapeake Bay where I fish. Looks like this method
will work for me and minimize the bubble risk with epoxy.

Thanks again.