The Alumaducer is a through the hull transducer. No need to cut a hole.That would most likely void the warranty on the center toon
I am thinking of installing it in the center tube or in the motor mount.I found it, not sure how it would work on pontoon. From the description I read, it sounds like it is for a traditional hull aluminum boat .
I would start by using the toilet wax method and seeing what locations work best before expoxying or other permanent adhesive. From the transom well you have good access to the undercarriage and be able to fish it up to the helm. If you're in the front storage area you might have to drill out to the helm side - I don't recall open an area to the underside of the deck (for obvious reasons). If you're in the rear of the storage area it will likely be occupied by your fuel tank and no easy way to get to the bottom. Good luck and please post results!
what's the toilet wax method? sorry for the noob question!
The wax acts as a liquid so the transducer can send and receive through it, and has the additional benefit of stickiness so the transducer will temporarily be adhered to the hull bottom while you test different locations.
A transducer can't send or receive through air so whatever you use has to be solidly connecting the ducer to the hull. You could build a little corral on the hull bottom and pour water into it, use vaseline or heck you could probably even use peanut butter! On the flip side you don't want anything that dampens the acoustics so I don't think using silicone would work. You'll read arguments for and against silicone online but I would imagine even if it did work, it would degrade the performance of your sonar. There's a reason why submarines have anechoic (rubber) tiles mounted on their hulls.