24v question

[Javelin JD]

I was initially going to place a 70lb trust trolling motor on my boat to replace teh 12v 45lb thrust that is on there. I took it out yesterday and the 45 that is on there trolls pretty well, however I still want to replace it with a new one, maybe upgrade to a 55 instead of the 70. My question is, would it hurt anything if I added the jumper to the trolling motor batteries and made it a 24v system. The front plug has three wires (black, white, and red), the old foot pedal has a selector from 12 to 24 volt, it has twin trolling batteries neither of which have a jumper attached. I don't have pics here but on a nother thread (possible Javelin rewire). thanks for the input