Batteries for Outboard Engines are unique and great care needs paid to what battery is used – otherwise, you may ruin your entire engine before you know it. It’s the Technician’s job to educate boaters, so here are some tips to help you do just that.


Manufacturer’s Recommendation

The minimum specification is for the motor alone, and does not consider other electrical requirements on the boat. Good rule of thumb is to add 20% to Mfg. Recommendation.

Quickest Testing Method

For a fully charged battery, the quickest test method is to crank the engine for approximately 15-20 seconds, with the ignition disabled. The battery should stay above 10.5 V if the engine is in good health and of proper capacity.

Unregulated Systems

On today’s digital electronics, over voltage can trigger shutdown or activate alarms. Avoid this by installing a heavier duty battery or install a second battery in parallel with a switch.

Recommended Maintenance

It is suggested to clean and secure battery connections, use lock washers & hex nuts tightened with a wrench, & Clean and spray connections with a non-hardening electrical sealer for protection.



CCA Cold Craking Amps = Maximum current output when tested at 0° F for 30 seconds.

MCA Marine Craking Amps = Maximum current output when tested at 32° F for 30 seconds.

RC Reserve Capacity = The number of minutes a battery can deliver a constant 25 Amps until voltage is decreased to 10.5V.

Group 24 is the most common marine battery size.


Starting – Designed for quick bursts of power, but if operated below 50% discharge, life is severely shortened.

Deep – Cycle – Designed for long term, low current draw, but are not designed for quick bursts of power.

Combo Start / Deep-Cycle – Designed to combine quick bursts of power & long term, low current draw.

Flooded-Cell – Designed to tolerate higher charging voltages.

Maintenance Free – *NOT RECOMMENDED for Marine Engines* Designed to minimize gassing during recharging, but are subject to early failure if the charging voltage is not regulated.

AGM – Designed to last long term, as long as they are not discharged below 50%.

Gel Cell – Designed to be very good for deep-cycle use, but very sensitive to charging currents & voltage limits.