How to Choose a Lithium Battery for Yamaha or Mercury Outboard Motors

Dakota Lithium Plus batteries are becoming increasingly common as starting batteries for car, truck, and boat engines. Especially outboard motors. Here’s 6 reasons why:

1. Dakota Lithium Plus batteries have over 1,000 CCA of cold cranking amps. That is twice the usable power in a smaller battery case than a comparable lead acid battery. Plus, the flat voltage curve means you have twice the usable capacity for deep cycle applications as well.
2. Dakota Lithium Plus batteries provide 10X the number of engine starts per charge. Dakota Lithium Plus batteries have a flat voltage curve. This means you can still start your outboard motors 10X as many times on one charge than a lead acid battery. Plus you can still start you engine 3-4 times even if your battery has <50% of capacity left, vs. a lead acid battery where you would be dead in the water at 50% capacity.
3. Dakota Lithium Plus batteries are 1/4 to 1/2 the weight of a comparable lead acid starting battery. That means better boat handling, improved hole shot, and more weight for the things that matter – fish, friends, and beer.
4. Dakota Lithium Plus batteries have 5X the lifespan of a lead acid starting battery. Dakota Lithium can be charged and used 3,000 – 6,000 times before capacity is reduced, vs. 500-600 times for a lead acid battery. Plus no corrosion, no watering, no toxic lead or sulfuric acid.
5. Backed up by an 11 year warranty.

Are lithium batteries compatible with my Yamaha or Mercury outboard motor?

Yes, a correctly sized Dakota Lithium Plus battery is compatible with all Yamaha and Mercury motors that are 250 hp or less. Here’s how to determine what size starter battery you need:

1. Determine the alternator output of your motor. You can find this in the manual for your motor, or in the technical specifications section of the web page for your motor.
2. If the alternator output is <71 Amps then the DL+ 12V 60Ah battery will work perfectly.
3. If the alternator output is >70 Amps but less than 165 Amps then the DL+ 12V 135Ah 1,000 CCA battery is the best fit. To protect the battery and ensure the longest lifespan the BMS cuts off charging at 80 Amps for the DL+ 12V 60Ah and at 200 Amps for the DL+ 12V 135Ah.

What lithium batteries are officially approved by Mercury outboard motors?

Mercury service bulletin no. 2022-19 officially approved the Dakota Lithium Plus 12V 135Ah dual purpose 1,000 CCA battery for use with these Mercury motors:

• 2.1L 75-115 HP-FourStroke, ProXS, and SeaPro, all serial numbers
• 3.0L 150HP FourStroke, ProXS, and SeaPro, all serial numbers
• 4.6L V8 and 3.4L V6 175-300HP FourStroke, ProXS, SeaPro, and Verado, all serial numbers
• 2.6L L6 200-400HP Pro and Verado
• 7.6L V12 500-600HP Seapro and Verado

Mercury motor approved lithium starter batteries that meet these following specifications for use with the above motors. Here’s what Dakota Lithium battery models meet these specs:

The DL+ 12V 135Ah 1,000 CCA battery meets or exceeds all specifications required by Mercury for use with the list of approved motors. It is the only Dakota Lithium battery approved for use by Mercury.

Customer experience has shown that smaller motors with HP below 200 generally have alternators <70 amps. This allows for use of the smaller DL+ 12V 60Ah battery. But erring on the side of caution Mercury only approved the largest lithium starter batteries even though smaller motors will work with a smaller battery.

Will using a lithium battery void my motor warranty?

The Magnuson-Moss Warranty Act states that outboard motor manufacturers are not legally allowed to void a warranty if a lithium battery is used to start their motor unless they can prove that the lithium battery in question caused or contributed to the failure in the vehicle. After 4 years of testing Dakota Lithium has no evidence that use of a lithium battery has caused a motor malfunction. The engineering is quite simple – motors require 12 volts to start. 12V coming from a lead acid battery and 12V coming from lithium battery are all the same electrons. That said, a battery that is too small for the alternator output of an outboard motor will cut off when the alternator starts charging. Make sure your battery is the right size for your motor or if in doubt choose a Dakota Lithium plus 12V 135Ah battery.

Troubleshooting: Lithium starter batteries and outboard motors

In our 4 years of testing various motors and lithium battery models here’s the top three problems our engineers encountered and their recommended solutions:

1. The battery is too small for the alternator and turns off when the outboard runs. Solution: make sure to check your user manual for your motor prior to purchase to see how many amps the alternator generates. If the alternator output is <71 Amps then the DL+ 12V 60Ah 1,000 CCA battery will work perfectly. If the alternator output is >70 Amps but less than 165 Amps then the Dakota Lithium Plus 12V 135Ah 1,000 CCA battery is the best fit. To protect the battery and ensure the longest lifespan the BMS cuts off charging at 80 Amps for the DL+ 12V 60Ah and at 200 Amps for the DL+ 12V 135Ah.
2. The outboard has an alternator that gives an inconsistent voltage that occasionally spikes above 15 volts and triggers the BMS in a lithium battery to turn the battery off (see below list of known motor models with this issue). Solution: These outboards are not compatible with any brand of lithium batteries unless an over voltage protection circuit is used. Contact sales@dakotalithium.com to request a over voltage protector / alternator regulator.
3. The battery is a deep cycle battery. Most lithium batteries are designed for deep cycle use only. Only a Dakota Lithium battery with a rating of 1,000 CCA should be used for starting an outboard. Solution: Use a battery with 1,000 CCA or more of engine starting power, such as the Dakota Lithium Plus 12V 135Ah 1,000 CCA battery

What outboard motors are NOT compatible with lithium batteries?

Some outboard motors have an alternator that gives an inconsistent voltage that occasionally spikes above 15 volts and will trigger the BMS in a lithium battery to turn the battery off. These outboards are not compatible with any brand of lithium batteries unless an over voltage protection circuit is used. If you have a motor on this list contact sales@dakotalithium.com to request a over voltage protector / alternator regulator.

[Insert Richard’s list of motors]

What battery do I need for my electric outboard motor?

Check the owners manual for your motor. Most electric outboard motors are 48V and would use the 48V 96Ah Dakota Lithium battery. Electric outboard motors are becoming a popular alternative to traditional gasoline outboards, especially on electric only lakes.