May have just what you need. Buyer of my last boat wanted Ulterra for walleye fishing. My 36V MG has one year of very gentle use. And have 36V Lester charger that may be a help for you, also.
I have a motorguide tour 36v for 250 OBO right now. It has been used and looks it, but still works well or did when I took it off. I had it on a 2004 courgar and it pulled it around great.