[Humanzee]

I'll throw in my $.02.

Ken makes some very good points spoken from experience, but I have a slightly different view on the battery's rating.

Deep Cycle describes the ability to be deeply discharged before being recharged. Starting batteries have a limited amount of times they can withstand a deep cycle.

In my opinion, the most important thing on a deep cycle battery is the RC and AH (amp hours). The RC is more accurate when used for high amp draw items like trolling motors.

The AH rating gives a better idea on how long a battery can carry lighter load, such as lights and electronics.

The RC rating is the number of minutes that a new, fully charged battery can carry a 25amp load at 80* Fahrenheit with a minimum voltage of 10.5 Volts. RC minutes are typically calculate using a 25amp discharge rate.

The AH rating tells you the number of amps that a new, fully charged battery can deliver at 80* F, multiplied by the number of hours, without falling below 10.5 V

Ex: A 100AH battery can deliver 5 amps for 20 hours (5 X 20 = 100). The 20 hour mark is a "generally accepted" time frame in the marine industry.

The higher the amp draw, the fewer total amps a battery can deliver. So that same 100AH battery cannot deliver 25 amps for 4 hours.

Some batteries will show you both the AH and RC. You'll see some differences. Said battery might show 100AH, and 150 RC. Not all batteries are linear.

For general comparison, here's Everstart (Cabelas) Deep Cycle:
Group Size 24 75AH 100RC
Group Size 27 115AH 160RC
Group Size 29 125AH 205RC

After running a bass boat for 20 years and trying my best to take care of my batteries, I'd definitely be looking for the highest RC I could find that'll work for my circumstances. Like Ken said, hauling a 45# battery versus possible a 65# battery back and forth gets old quick.