You might want to think about a second battery.
The larger the trolling motor the more power it will take.
The first time I took a small plastic boat out with my 55# I was a fat and happy camper---until it was time for me to head to the ramp. The motor had drawn the battery down so the trolling motor was only able to propel the boat about as fast as I cold swim. Not a good feeling. Second battery helped me stay out on the water much longer.
If it gets windy, you may end up using more of the battery than you had planned.
If I remember correctly the 55# would push the boat about 4.5 - 5.0 MPH using a GPS when the battery was at full charge.