What Size Battery for A 90 HP Outboard?

Published on: December 5, 2022
Written by Jonas Frank / Fact-checked by Nova Scarlett

A 90 HP outboard motor typically requires a 12-volt marine battery with a minimum of 110 amp hours. The ideal battery size for a 90 HP Johnson outboard is a group 24 or 27 deep cycle marine battery.

Selecting the right battery for an outboard motor is essential for optimal performance and reliability. For smaller motors, like a 9.9 HP outboard, a lighter battery, such as a group U1, may suffice. Mercury outboard motors have specific battery requirements, often needing a robust, deep-cycle marine battery to handle their power demands. The best battery for a 25 HP outboard motor should combine sufficient cranking amps with deep-cycle capabilities to ensure consistent performance.

what size battery for a 90 hp outboard

Yamaha outboard motors, including the popular Yamaha F70, often require specific battery sizes and types to function effectively. A group 24 marine battery is typically suitable for these models. For larger motors, such as the Johnson 150 outboard, a more powerful battery, like a group 27 or 31, is recommended to handle the higher starting and running loads.

For mid-range motors, such as a 50 HP Johnson outboard, a group 24 battery usually provides the right balance of size and power. It’s essential to consider both the starting (cranking) and deep-cycle requirements of your outboard motor when choosing a battery.

For more detailed information on selecting the right battery for your specific outboard motor model and usage requirements, we invite you to read the detailed article below. This guide will help you make an informed decision, ensuring your outboard motor runs smoothly and efficiently.

Choosing the Right Battery for Your 90 HP Outboard

Battery Types for Outboard Motors

Lead-Acid vs. Lithium-Ion Batteries

When it comes to powering your 90 HP outboard motor, the type of battery you choose plays a pivotal role. Lead-acid batteries have been the go-to choice for years, known for their reliability and cost-effectiveness. They’re heavier but do the job well. On the other hand, lithium-ion batteries are the new kids on the block. They’re lighter, charge faster, and have a longer lifespan, but they come with a heftier price tag. It’s like choosing between a reliable old truck and a flashy new sports car – both have their perks!

Deep Cycle vs. Starting Batteries

Now, let’s talk about deep cycle versus starting batteries. Deep cycle batteries are marathon runners; they provide a steady amount of power over a longer period. They’re perfect for powering your onboard accessories. Starting batteries, in contrast, are sprinters. They give a quick, powerful jolt to start the engine but don’t last long under continuous use. For a 90 HP outboard, you might lean towards a deep cycle battery for its endurance, especially if you love those long days on the water.

Size Recommendations for 90 HP Outboards

Standard Battery Sizes and Their Capacities

Choosing the right size for your 90 HP outboard is like picking the perfect pair of shoes – it needs to fit just right. Generally, a group 24 or 27 marine battery is a solid choice. These batteries offer a good balance between size and capacity, ensuring your motor has enough juice to keep running smoothly without taking up too much space.

Battery Size Comparison for Different HP Outboards

HP RatingRecommended Battery SizeApprox. Amp Hours
Up to 50 HPGroup U135-40 Ah
50-70 HPGroup 2470-85 Ah
90 HPGroup 2785-110 Ah
Over 100 HPGroup 3195-125 Ah
visual chart (1) battery capacity calculation examples
visual chart (1) battery capacity calculation examples

Power Requirements for Optimal Performance

Calculating Ampere-Hour Needs

To keep your 90 HP outboard running at its best, you need to know how much power it needs. Think of it like figuring out how much fuel your car needs for a road trip. The ampere-hour (Ah) rating tells you how much electricity a battery can supply for a certain period. For a 90 HP motor, you’re looking at a battery that can deliver around 85-110 Ah. This ensures your motor won’t run out of steam in the middle of your adventure.

Cold Cranking Amps (CCA) for High-Performance Motors

Cold Cranking Amps (CCA) is another key factor, especially in colder environments. CCA measures a battery’s ability to start an engine in cold temperatures. For a high-performance 90 HP outboard, a higher CCA rating means a smoother start on those chilly mornings. It’s like having a good cup of coffee to kickstart your day!

Brand-Specific Battery Needs

Yamaha 90 HP Outboard Battery Specifications

If you’re sporting a Yamaha 90 HP outboard, you’ll want to pay attention to the manufacturer’s specifications. Yamaha often recommends specific battery types and sizes to ensure optimal performance. It’s like following a recipe to the letter to get that perfect cake!

Mercury and Johnson: Special Considerations

Mercury and Johnson outboards might have their own set of requirements. These brands might need batteries with higher CCA ratings or specific dimensions to fit snugly in the motor’s battery compartment. It’s always best to check the manual or consult with the manufacturer to avoid any missteps.

Brand-Specific Battery Requirements

Outboard BrandRecommended Battery TypeMinimum CCA
YamahaDeep Cycle380 CCA
MercuryDual Purpose (Deep Cycle/Starting)400 CCA
JohnsonStarting450 CCA
90 HP (General)Deep Cycle385 CCA
visual chart (2) brand-specific battery requirements
visual chart (2) brand-specific battery requirements

Installation and Compatibility

Ensuring Proper Fit and Connectivity

Installing your battery is more than just plugging it in and sailing off. You need to ensure it fits well in the battery compartment and that all connections are secure and corrosion-free. It’s like making sure all the pieces of a puzzle fit perfectly to complete the picture.

Voltage and Compatibility with Boat Electronics

Also, consider the voltage and its compatibility with your boat’s electronics. A mismatch can lead to poor performance or even damage your equipment. It’s like making sure you have the right adapter for your electronics when traveling abroad.

Maintenance and Longevity of Marine Batteries

Regular Maintenance Tips

To keep your battery in tip-top shape, regular maintenance is key. This includes checking fluid levels, cleaning terminals, and ensuring it’s charged. Think of it as regular check-ups to keep your battery healthy and long-lasting.

Extending Battery Life

You can also extend your battery’s life by avoiding deep discharges and keeping it in a cool, dry place when not in use. It’s like taking good care of your favorite gadget to ensure it lasts longer.

Maintenance Schedule and Tips

Maintenance TaskFrequencyTips
Check Fluid LevelsMonthlyTop up with distilled water if low
Clean TerminalsEvery 3 MonthsUse a brush and baking soda solution
Regular ChargingAs NeededAvoid letting the battery fully discharge


Can I Use a Car Battery for My 90 HP Outboard?

Using a car battery for a 90 HP outboard motor is not recommended. Car batteries are designed to deliver a high current for a short period to start an engine, known as cranking batteries. They are not built to withstand the deep discharge cycles required by boat motors. Marine batteries, on the other hand, are designed to provide a steady current over a longer period, which is essential for the consistent operation of an outboard motor. Additionally, marine batteries are built to endure the harsh marine environment, including vibrations and potential exposure to water, which car batteries are not equipped to handle.

What Is the Impact of Battery Weight on Boat Performance?

The weight of the battery can significantly impact the performance of your boat. A heavier battery might provide more power, but it also adds to the overall weight of the boat, which can affect its speed and fuel efficiency. For a 90 HP outboard, it’s crucial to strike a balance between battery power and weight. Choosing a battery that provides sufficient power without excessively adding to the boat’s weight will ensure better handling, speed, and efficiency. Lightweight options like lithium-ion batteries can be beneficial, offering adequate power with less weight compared to traditional lead-acid batteries.

Does Battery Placement Affect Boat Balance?

Yes, the placement of the battery in your boat can affect its balance and handling. Ideally, batteries should be placed in a location that helps maintain the boat’s center of gravity. Improper placement can lead to uneven weight distribution, affecting the boat’s stability and handling. For instance, a battery placed too far aft or forward can cause the boat to trim incorrectly, impacting its performance and safety. It’s essential to follow the boat manufacturer’s guidelines for battery placement to ensure optimal balance and performance.

How Does Temperature Affect Battery Performance?

Temperature has a significant impact on battery performance. In cold conditions, a battery’s chemical reaction slows down, reducing its efficiency and making it harder to start the engine. This is why a higher Cold Cranking Amps (CCA) rating is essential for colder climates. In contrast, high temperatures can increase the rate of chemical reactions inside the battery, leading to faster wear and reduced lifespan. It’s important to choose a battery that can operate efficiently in the temperature range you typically boat in and to take steps to protect the battery from extreme temperatures.

What Are the Environmental Considerations for Battery Disposal?

Disposing of boat batteries requires careful consideration due to their environmental impact. Lead-acid batteries, commonly used in boats, contain harmful substances like lead and sulfuric acid. Improper disposal can lead to these substances leaking into the environment, causing soil and water contamination. It’s essential to dispose of batteries at designated recycling centers where they can be processed safely. Many areas have regulations and programs in place for battery recycling, so it’s important to be aware of and comply with these to minimize environmental harm.

How Do I Know When to Replace My Boat’s Battery?

Knowing when to replace your boat’s battery involves monitoring its performance and condition. Signs that a battery needs replacing include difficulty in starting the engine, the battery not holding a charge, or visible damage such as swelling or leaks. Regular testing of the battery’s voltage and load capacity can also indicate its health. Typically, marine batteries last between 3 to 5 years, but this can vary based on usage, maintenance, and environmental conditions. It’s advisable to have a routine check-up of your battery as part of your regular boat maintenance to ensure it’s in good condition.

Can I Use Multiple Batteries for My 90 HP Outboard?

Using multiple batteries for a 90 HP outboard can be beneficial, especially if you have high power demands or want a backup system. This setup usually involves one battery for starting the engine and another for running onboard electronics, known as a dual-battery system. It ensures that the use of accessories doesn’t drain the battery needed to start the engine. When setting up multiple batteries, it’s crucial to use a battery switch and ensure that both batteries are compatible in terms of voltage and capacity. Proper installation and wiring are key to the effective functioning of a dual-battery system.

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