Hi guys. I have an old marine battery that seems to be dying.  I'm looking for a new one to run my 28lb Minkota trolling motor on my 10 foot bass raider pontoon boat.  Any suggestions on which one to get without spending hundreds?  

Also, I use a basic battery tender on it.  Is there something I should get that will increase the life of the battery like a maintainer, more than just one of those batter tenders?  Thanks.

Walmart group 29 marine battery is a good one. A little over a 100 bucks

Only buy a deep cycle battery not a cranking battery.  The amount of time you get to spend using the trolling motor is directly related to the Reserve Capacity of the battery.  The larger the RC number the longer it will hold up during the day.

Deep cycle from Walmart or Auto Zone,

I use Exide deep cycle marine batteries from Menards

I switched from Walmart to Interstate a couple years ago and couldn't be happier.