NO! don't waste your time with the Group 27, it's too heavy takes to long to charge and there's no place to put it. Use 2 NF-22 AGM 55Ah batteries ,that gives you 110Ah's, they can be stowed inside the center hatch under the seat between the scupper tubes, it's a perfect fit with maybe 1/16" clearance and I use a bungee cord to secure it, this also gets some of the weight off the bow of the 12, which will make it handle better.
Use your pedals to get there and the motor to fish, fishing without the motor sucks, you have very little control, and you have no reverse. When you use the motor you see the flaws in peddling