question about transducers

[bridgeman]

I have a furuno fcv 620 and need to get a tranducer, not really wild about drilling any more holes than neccessary in the transome so I thought about getting a shoot thru hull design but when I researched it stated that it won't work on cored hulls (don't know if I have a cored hull) don't feel comfortable drilling a large hole in the bottom of the boat to install a thru-hull. Don't know what to do at this time and have to make a decision in the next few weeks, thinking maybe a transome mount on a mounting board sealed with 5200 is the way to go.