Maybe my old 80# Terrova needs service but I definitely gave it a work-out yesterday. I only have a 16' aluminum boat, but it was 2.5mph into the white caps, pulling 6 lines. I did have the Yamaha providing a little forward motion, but the Minn Kota had to go to full power most of that 6 hours just to maintain the direction.
On calmer days, it will only require about half power and will last 16 hours plus. And since mine is a 24v system, my two 100 ah batteries in series only give me 100 ah, compared to your 140. Are you trolling with your Minn Kota? How big is your boat?