I installed a 60" 80lb thrust 24v on my bow. When fully deployed it is about 18, 20" under the water. It would be a lot further down if I'd mounted it to the back because of how the boat tilts, but of course it has a collar stop on it to set the desired deployed depth.
I don't like it on the bow though; it is in the way when deployed, hard to walk around, and when it is stowed it is REALLY in the way sitting down on the deck. I'm planning to move it to the rear (that will be a new thread sometime).
I'm new here and new to pontoons so please take this with a grain of salt. I am sure there are great veterans here with better information. I'll be leaning on them myself if I can.