With a boat your size upping the TM thrust will not be as much benefit as the extra battery you will have aboard the boat.

12v 48#, 24v 80#, 36v 109#. Each step adds a battery to the equation. Will you ever use the 109# of thrust? Occupationally when you don't want to power up the outboard to move from here to there. But I bet some day you will be grateful you have the extra reserve capacity you get with each battery. In most cases you will be using the same amount of thrust depending on wind and fishing style at the time. Fishing thought flooded timber using 25# of thrust. Any of the TM i listed will work fine. If you have a 36v system you will be able to do this 3 times as long as the 12v system. If you are going to pull cranks using 45# of thrust the first TM will still do this but not for very long. Again the 36v system will get you three times as much time fishing this style.

Main lesson here is the amount of thrust needed is seldom what we should be looking at. The amount of battery reserve you need to accomplish the style of fishing should be at the top of your list.

Good luck