I just put a new Terrova on my boat. I have a 17'-6" deep V Tracker.
I opted for the 12v 55# 54" shaft. Here's why
-I went with the MK because of the remote. The MK's have a screen on the remote so you can see what's going on. With a MG there is NO SCREEN ON THE REMOTE so you'll have to link it to you electronics in order to see what's going on.
-I looked at the 12v vs the 24v and was going to go with the 24v but before buying I emailed MK and asked if there was a down size to overpowering a TM on my boat. Their reply was to NOT overpower because they said the spotlock performance could suffer. Spot lock was the main reason I upgraded the TM. On the MK website there is a boat weight VS thrust formula that MK advised I follow. (at least 2# of tm thrust for every 100# of fully loaded boat) I followed their recommendation.
-On a 12v you have a choice of a 45" or 54" shaft. On a 24v your choice is 45" or 60" shaft. The 45" only has 32" of shaft below the bottom of the mount, so it's way too short. I really did not want that 60" shaft available on the 24v.
Now I've only used my TM 3 or 4 times but I have to say I love it so far. I had a cable steer before this so getting used to the electric steering is taking a little getting used to but I'm getting there. The spot lock is fantastic and we've used in winds up to 20 mph and swirling/gusting. Mind you it's not perfect but it is way better than I could ever do and even better than using an anchor. The 12v has plenty of power for me and I do have 2 batteries on the boat. Most of my fishing sessions last 6-7 hours and I haven't put a dent in the batteries yet.
So far no regrets for me.