Here’s my take, I have an Alumacraft Tournament Pro 170 with a 60HP tiller. My boat has a 24V 65# power drive and does very well, lasts along time and can move the boat faster than I need. The nice thing with a bigger motor is that you can run it at a slower speed, thus making it last longer and not work as hard.
My Dad’s boat is a 1600 Lund predator with a 50hp tiller. His boat had a 12V 45# power drive and it was doggy, you had to run it at a high speed to keep the boat moving in any wind. I found a used 55# power drive that had a bad board for $25 on craigslist, I took the motor off that and put it on his. It’s better but still not the best.
One thing to note is you can always hook another battery up to your 12V system and have more capacity with the 12V, but I think you’ll be wanting to upgrade before long.