What Size Battery For A 90 HP Outboard? A Complete Guide

What size battery for a 90 hp outboard?
What size battery for a 90 hp outboard?


When it comes to powering your 90 horsepower outboard motor, selecting the correct battery size is crucial for optimal performance and a hassle-free boating experience. Many boat owners often wonder, “What size battery for a 90 HP outboard?” In this guide, we will provide you with the information you need to make an informed decision and keep your boat running smoothly on the water.

Understanding the Basics

Before we delve into the specifics of choosing the right battery size, let’s briefly cover some essential concepts.

  1. Battery Types: Marine batteries come in various types, including starting batteries, deep-cycle batteries, and dual-purpose batteries. Understanding the differences between these types is crucial in selecting the right one for your 90 HP outboard motor.
  2. Amps and Voltage: Batteries are rated in terms of ampere-hours (Ah) and voltage (V). Ampere-hours represent the battery’s capacity, while voltage indicates its power output. For a 90 HP outboard, you’ll typically need a 12-volt battery.

Choosing the Right Battery Size:

Now, let’s address the key question: “What size battery for a 90 HP outboard?”

  1. Cranking (Starting) Battery: For starting your 90 HP outboard motor, you should choose a cranking battery. These batteries are designed to deliver short bursts of high power to start your engine. A common choice for a 90 HP outboard motor is a Group 24 or Group 27 cranking battery. These batteries offer the necessary cold cranking amps (CCA) to get your engine running smoothly.
  2. Deep-Cycle Battery: In addition to a starting battery, you may want to consider installing a deep-cycle battery. These batteries are designed to provide a steady supply of power over an extended period. Deep-cycle batteries are perfect for running accessories like fish finders, trolling motors, and lights on your boat. Depending on your power needs, you can choose a battery with a suitable ampere-hour rating, typically ranging from 50Ah to 100Ah or more.
  3. Dual-Purpose Battery: If you want a more versatile option, dual-purpose batteries can serve both as starting and deep-cycle batteries. While they might not excel in either category compared to dedicated batteries, they provide a convenient compromise if you have limited space on your boat.

Maintenance and Care

Once you’ve selected the right battery for your 90 HP outboard motor, it’s essential to maintain it properly:

  1. Regular Charging: Charge your batteries regularly, especially during the off-season or when not in use. Consider investing in a quality marine battery charger to ensure the longevity of your batteries.
  2. Battery Storage: Store your batteries in a cool, dry place and keep them clean and free of corrosion. Inspect them for damage or leaks regularly.
  3. Safety: Follow safety precautions when working with batteries, including wearing protective gear and avoiding sparks or open flames.


Selecting the correct battery size for your 90 HP outboard motor is vital for reliable performance on the water. A combination of a cranking battery for starting and a deep-cycle battery for accessories is often an excellent choice. Be sure to consider your specific needs, maintain your batteries regularly, and follow safety guidelines to ensure a trouble-free boating experience. With the right battery, you’ll enjoy smooth sailing and worry-free adventures on the water.

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