My yak has a cutout beneath for a transducer, but I chose not to use it. Within a few years, seems all electronics sooner or later go on the fritz. Then the companies that tout their "best" product refuse to repair them, but instead steer you to trade in for a discount. Rather than dealing with silicone or any other goop, I used this:
https://www.amazon.com/YakAttack-RAM%C2%AE-Long-Transducer-Mount/dp/B01K5ODHUK
Changing out to a new tranducer is a cinch, besides the added benefit to swinging directly into the craft when traveling through reeds, heavy pads, or landing. The whole device can be removed easily when there's no need for the fish finder.
There's a through hull magnet mount that looks neat too, but seems a bit pricey.
https://www.fishfindermounts.com/transducer-mounts
