i have a pro 175 tf and have a 12v Minn Kota® Edge 45lb  and want to go to a 24v minn kota 65 or 70lb what do i have to do to convert my boat so it will be a 24v sistem........ or can i just bridge the batterys and keep everything the same.

Verify wire gauge vs length of run vs motor amp draw http://www.minnkotamotors.com/Battery-Selection-Rigging/

Check your wire first, but most of the time you can just add the jumper wire in the back instead of running more wires. 

thanks for the help. 

Don't know what year your boat is but when I had my 2009 Tracker PT190, I called Tracker and spoke with them about this. The boats are wired with 8 gauge which is sufficient to power a 24V TM up to 45 amps. All you need to do is add the second battery. Most TM's up to 80 lbs of thrust won't exceed a constant  45 amp draw. Some guys will tell you that you need to rewire with 6 gauge. Not true. I did a lot of research on this.