Andy,
Have you tried temporarily installing it to see if it will work without removing the foam? If it's a shoot-thru-hull, that you mean, and not a thru-hull you may find that at the hull area near the transom that the unit simply works. Shoot-thru transducers are mounted inside the boat, and the energy passes through the fiberglass and foam. They are typically higher power -- usually 600-1000w given that they have to pass through the fiberglass in both directions. Air in the foam can attenuate the signal making it useless, however, many boats don't use foam at the deepest part of the V-hull (my current and last boat use a shoot-thru transducer, and there was no need to remove the foam). Use a bucket, or a small plastic container (like Tupperwear) with a smooth flat bottom (so the signal doesn't have to pass through the air), fill it with water and put it, and your transducer into it in the position you want to install it -- a couple dabs of silicon and it will hold in place temporarily. Do some driving around and see if it works.
If it's an actual thru-hull where you are cutting a hole in the bottom of your boat, then I'd go to a good dealer -- Gartside in Sidney can likely take care of it and it's not to far...
