Trolling Motor Batteries Charging/Boiling

[Cabela10]

I have 2 Trojan 27 group batteries running my trolling motor and a Minn Kota 3 bank charger charging those 2 TM batteries plus the starting battery. I noticed today once the batteries were charged, that the TM batteries were popping. Is this just the water/acid being hot and boiling? I've never had problems with these batteries and running with them all day with TM on high. Please help.

[Whoaru99]

It's normal for flooded cell batteries to bubble when being charged.

Did you feel them - their temperature, that is? It's not unusual for batteries to get warm when being charged at a medium/high rate, but really shouldn't be hot, per se.