When you're shopping for marine electrical batteries lighting, the first decision isn't brand-it's how much battery your boat can hold and what that battery needs to do. A dedicated starting battery maximizes cranking amperage; a dual-purpose battery also runs trolling motors and accessories when the engine is off. That's exactly the fork you face with the ACDelco M31AGM Marine AGM and the Interstate Batteries Marine/RV Group Size 24 Dual Purpose AGM. Both are new AGM options, but they solve different problems.
Quick verdict
If you want maximum starting muscle, the ACDelco M31AGM is the workhorse. If you need one battery to crank the motor and then power trolling and accessories, the Interstate Marine/RV Group 24 is the versatile pick.
Key differences at a glance
| Feature | ACDelco M31AGM Marine AGM | Interstate Marine/RV Group 24 AGM |
| Price | USD 159.09 | USD 259.95 |
| Case / type | Group 31 AGM | Group 24M AGM |
| Cold cranking amps | 925 CCA | 750 CCA |
| Capacity / reserve | RC 200 minutes | 70 Ah, 140 RC, 940 MCA |
| Dimensions | 13.1" x 6.8" x 9.1" | 11" x 6.81" x 8.98" |
| Best for | Bigger engines and longer reserve | Starting plus trolling in one battery |
Where each wins
The ACDelco M31AGM wins for boaters who put starting performance first and want a battery that can handle more than just a crank. The Interstate Marine/RV Group 24 wins for boaters who need a single battery to both start the motor and power their electronics and trolling gear on the water.
ACDelco M31AGM Marine AGM
The ACDelco M31AGM brings 925 CCA and a 200-minute reserve capacity to the table, which makes it a strong choice for boats that need reliable starts even after sitting. The dual marine terminals simplify hooking up extra wiring, and the vibration-resistant construction is a plus on rough water. If your boat's battery tray is sized for a Group 31 battery, this is a straightforward upgrade with a lot of starting power. The limitation is the case itself: at over 13 inches long, it will not drop into a Group 24 tray, so you need to measure your compartment before ordering.
Interstate Batteries Marine/RV Group Size 24 Dual Purpose AGM Battery
The Interstate's selling point is the dual-purpose 70Ah rating: it is built to start your motor and keep power flowing to trolling motors and marine electronics when the engine is off. That makes it a good fit for smaller boats where a single battery has to do everything. The 940 MCA supports cranking while the 70Ah capacity gives you usable accessory runtime. What holds it back is the price: at $259.95 it costs significantly more than the ACDelco. If you're trying to stretch every dollar, that higher price is the tradeoff for the dual-purpose convenience.
Final choice by use case
Choose the ACDelco M31AGM for starting-first setups where you want maximum cranking confidence. Choose the Interstate Marine/RV Group 24 for dual-duty setups that need to start a motor and power trolling gear from the same battery.
