I just got a used prowler 30 lb thrust trolling motor and I have a few questions that I wasn't able to find elsewhere on this forum. How long could I run it on the maximum speed without it messing up on me? What battery could I get for it ? I have a small budget and I'm wondering if this one would work: http://m.ebay.com/itm/251332503272?nav=SEARCH Would this one be okay if it came in contact with a little water? What is the difference between this battery and the other batteries made specifically for trolling motors? Any help would be greatly appreciated.

Honestly, that battery isn't going to run your trolling motor very long. If i were you i would get a deep cycle Everstart from walmart, cost a little more but worth it. They have one that should run your trolling motor for several hours for around 59 dollars. but if you can swing it, for $100 you can get an everstart maxx that will run it all day. 

Ive been using Sears Die Hard Deep Cycle batteries for years. The group size 27 costs around $100. The only downside is it's a ''wet'' battery and you will have to check the fluid level from time to time. Run time will depend on things like the size of your boat and battery, wind and current and how good your charger is.

Honestly, that battery isn't going to run your trolling motor very long. If i were you i would get a deep cycle Everstart from walmart, cost a little more but worth it. They have one that should run your trolling motor for several hours for around 59 dollars. but if you can swing it, for $100 you can get an everstart maxx that will run it all day. 

I have a 29 cer Everstart from Wal-Mart cost about 89.00 and it pulls my 20 foot pontoon boat around all day with plenty of power

I have a 29 cer Everstart from Wal-Mart cost about 89.00 and it pulls my 20 foot pontoon boat around all day with plenty of power

This is going to be the best bang for your buck. I believe it also has a 20 month replacement warranty

Trolling motors use deep cycle batteries and the ones that last longest are usually the heaviest lead/acid model you can fit in your boat.  The small battery you cite would probably run the TM for 30 mins.  A size 27 deep cycle motor would weigh in at around 70-80 lbs and run it all day, depending on the size of your boat.