Adam created this magnetic mount for boats and kayaks. The great thing about this project is that it allowed him to mount this transducer (we assume he’s using this as a depth/fish finder) to the side of his boat without having to drill any (more) holes into this kayak. It also allows him to switch is quickly and easily between boats. Great for rentals!
The magnets themselves are really strong. Over 65 pounds of pull strength. This is necessary to create the bond through the hull. You wouldn’t want a project like this disconnecting and falling to the bottom of the lake. At least you’d know how deep it is… ;)
You can also read Adam’s extended write-up on Instructables.