Chipppo posted a nice idea how to avoid putting holes to mount a transducer in larger transoms. Here's one that allows the transducer to be attached and detached in less than a minute:
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The brass attachment is from the dollar store to hang wreaths.
The clamp is from Tractor Supply or any place that has hardware supplies.
The wood I had hanging around which used to be a stake.
Zip ties help stabilize the brass.

Been using this attachment for a few years and never had a problem plus the boat can barge through weed and the transducer positioned above the hull's bottom never picks weeds up.

Note: I also use the brass plate to hold my oars when not in use.