Well, to truly check a battery, you need to check the specific gravity of each cell. Pick up a gravity tester (around $8 at any parts store) and follow some of these instructions:
http://www.trojanbattery.com/BatteryMaintenance/Testing.aspx
Please wear safety glasses and basically, you just pull up some of the electrolyte from each cell and get a reading. You can check state of charge that way and test for a bad cell too. If all the readings are similar, most likely the cells are all good. If all are up but one is down, you have a bad cell. Pretty easy and straight forward.
The link above shows what the readings should be on a fully charged battery.
So, charge them, let them cool and then test them. Then, go fish and test them again after to see what the state of charge is after use.