What you usually see
Interstate flooded marine batteries are common on trailer bass boats and as starting batteries on lake skiffs. Group 24, 27, and 31 cover most trays we open. Factory codes change by year and warehouse. The useful facts at the boat are the BCI group size printed on the case, whether the battery is labeled starting or deep-cycle, and whether the cells still take water.
Flooded care in Florida heat
These are vented wet cells. Heat drives water loss. Caps that have not been opened in a season, a box with no airflow, and a charger that never rests are the usual combination. We check electrolyte where it is safe to do so, and we do not treat a flooded Interstate as a sealed pack you can bury under a seat and forget.
Trolling strings
A 24- or 36-volt bow bank needs matching type, age, and capacity in series. Replacing one Interstate in a three-battery string and leaving two tired neighbors is a short repair: the new cell works harder and sulfates with the rest. Battery University’s series/parallel notes are the same on a bass boat as in a lab.
Lines we are asked about
Model names below are public line names used to identify batteries already on boats.
- Marine group 24 — Common starting size on smaller outboards and tight consoles.
- Marine group 27 — Starting or deep-cycle marine, depending on the specific flooded line.
- 27M-XHD — Interstate published marine starting battery in a group 27 envelope (see Interstate marine starting).
- Marine group 31 — Larger starting or trolling flooded marine, heavy, needs a 31 tray.
- SRM-31 — Interstate published marine deep-cycle battery in a group 31 envelope (see Interstate marine deep-cycle).
We replace marine batteries at the boat. See services and what changes a quote.