I have the12 volt Terrova on my 16.5 ft Bass Tracker. It is worth every penny, I can't imagine fishing without it, especially when you are by yourself or have kids on board. I know I will get kick back when I say this, but the 24 volt would have been a waste of money for me. I mostly tight line, but also pull jigs. These motors have "Maximizer" circuitry in them which gives you very efficient battery drain. I have run mine 6 hours nonstop and was down only about 50%. I guess my boat is lighter than most because I seldom run more than 40% of the maximum speed. Wide open it will pull my boat about 6 or 7 MPH which is way faster than I ever need to go with the electric motor.
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I also have the regular length shaft and I have it set up about a foot short of the maximum depth and it has never cavitated on me, but I don't fish in high wind and waves. That is a nightmare when you got 6 or 8 12ft. rods hanging off the front. I did get the universal transducer which made it easy to hook up the front DF. Oh, yea I strongly recommend the quick release mounting puck that Minnkota makes. It makes it a snap to remove your motor if you need to and greatly simplifies installation.
If you have 2 boats it is easy to move back and forth using the mounting pucks.
So, go with whatever you feel will suit your needs, but the Terrova is well worth the cost, whichever model you get