Hi Stephen
Bonded the 178 fish-finder head to the hull on Cleo yesterday
I made a wooden "bath" and set it in silicone to make a reservoir last week
i then placed to transducer head in it and poured 2pack Sp epoxy with heavy on hardener to speed up setting process, press down to remove any air bubbles andplaces a brick to hold down
When i turned GPS on i got a clear reading of the bottom through the hull although it is flat (cant leave the mooring as engine in bits for another week or so) also compared the depth with the echo sounder with about 6 inches differences
water temp was 45 Degrees F but no way to see if accurate thru the hull!
so all in all it seems to work
will let you know when impeller and oil back in engine and can go for a sail to see if works 100per cent
Cheers
Peter