Airmar is the manufacturer of most of the shoot thru hull transducers. They no longer reccomend the two part epoxy. I would go to
www.airmar.com and look up the instructions for the unit you have. It might be the P-79. Does the transudcer sit in a cup with markings on it for your boats deadrise angle?
If its the cup, you have to seal the cup to the hull with 5200. Then you fill the cup with oil (I think its mineral oil or whatever they use for constipation) then you put the tranducer in the oil bath sealing it to the cup.