So I neglected my 4 group 27 house bank batteries fluid level. I ended up adding about a quart of distilled water to each one. It was hard to get a good view, but I think the fluid level was below the plate tops on a few cells. Anyway filled them up, turned on the charger and was back at the boat 24 hours later. Noticed that charger monitor was reading 5 amp charge input. Turned off the charger and went to check the voltage at the terminals. One battery was hot (guess around 120 F ) disconnected it from the bank and got 8.5 volts at the terminal. Disconnected another battery and got 12.7 at terminal. Didn't check the other two. I now have a replacement to install for the hot battery. Bank is 7 years old.Do I have to replace the other three batteries? Or will installing 1 new battery in a four battery bank shorten the life of the new one? The new one is a direct replacement of the old one, lead acid same specs, same manufacturer. Can I replace the other three when I get to it? They are a bear to get out. Probably will only put a few days of deep discharge cycles on the bank the rest of the summer.