I believe any transducer is a "through hull" if it's epoxied to the inside
of the hull. GRP has the same sound velocity as water and there is almost no
signal loss. I know one boater who glued it to the inside of the wooden keel
of his boat. It worked fine, even though it was "looking through" 14" of
wood.

Bruce




"Courtney Thomas" wrote in message
...
Economy and durability are being sought here.
Thank you.
--
Courtney Thomas
s/v Mutiny
lying Oriental, NC