One of the biggest advantages of a 24 or a 36 volt over a 12 volt motor is simply more pounds of thrust.Alot of it depends on the way you'll use your trolling motor,how often, and how big your rig is.You wouldn't want to put a 12 volt motor on say a 20 foot boat.You'd probably wouldnt have enough power to fish all day, or if you add any wind or current, it wouldnt be effective.We'll generally install 12 volt motors on 16 foot and smaller boats.17 footers your'e starting to get more towards a 24 volt system, if its a lighter one and you wont use it very often a 12 volt might suffice.Anything over 18 foot I seriously recommend a 24 volt system and 19 foot and larger either a 24volt or for a heavy user a 36 volt.Hope this helps you out.PJ