60 HP Mercury Outboard Battery Question

[macowneril2015]

So I recently had some starting issues with my 2023 60 hp mercury outboard and was considering the batteries may be bad as they are older. I have 2 size 27 AGM dual purpose batteries. Upon researching I saw that Agm batteries were dangerous for this engine due to a stator vs alternator and can lead to over working of the charging system. I was unsure if others have had any issues? I preferred AGM as there is a less of a venting concern vs lead acid. My boat has shore power and I keep the batteries in a pro mariner smart charger. Any help or thoughts on batteries are appreciated.

https://www.bbcboards.net/showthread.php?t=1249598

^above link is what I am citing, what is ironic is I have the same model of engine.

[kurz]

I would not mind.
I use a AGM type starter bat for 10 Years. And now I use a lifepo4 (winston) for 2 years. No modification of the charging system.

I guess thousends of AGM-types of batteries run with these ob's...

[OverEasy]

Hi Macowneril2015!

There is a similar type of requirement by Suzuki for batteries:


So your Mercury requirements/recommendations aren’t alone.
Given that the OEM has a vested interest in the performance, longevity and durability along with customer satisfaction I doubt these recommendations were done lightly. The OEMs have actual engineers and practical development personnel with lots of experience to back them up. They want you to have a great and trouble free experience with your engine. I’d stick with the OEM recommendations, especially since you’re looking to get a new battery anyway.

Personally I’m in favor of a dual battery arrangement with use/charge isolation switches and either a positive post or circuit breaker to be incorporated. The fuse or circuit breaker will help mitigate the risk of a deal short of the power leads between the battery(ies) and the engine (should those leads ever become compromised (pinched, fretted, etc…).

I’ve towed others who had single battery systems drained by trolling motors, radios, etc…..
(As a young teen I drained my dad’s car battery flatter than the bottom of a cast iron fry pan in the backwoods of Vermont listening to the first Apollo Moon Landing…. It was a REALLY long hike with a battery to where we could get it charged up again…a longer hike back too! Didn’t do that again! … I would have dearly loved to have had an isolated second start battery… Really! )

Your boat / Your rules

Best Regards
Over Easy

PS: I think my arm lengths matched those of an orangutan by the end of that day … and that was AFTER I made a drag stretcher to carry the charged battery for the trip back….

[Be Free]

There is not a big difference in the charge profile of a FLA vs AGM battery. The FLA prefers a higher voltage and a lower amperage and the AGM is the opposite. An AGM will be able to take any amperage that an FLA is happy with.

Where you might have an issue is with voltage. AGM batteries do not like to be charged above 15V. According to one source I was able to find, the expected voltage for your engine should be 13.7-14.5 volts (well withing safe AGM limits). Check yours when it is running. If it is not over 15V then AGM should be fine.

The chemistry in and FLA and AGM battery is identical. The only difference is that the sulfuric acid is Absorbed in a fiberGlass Mat instead of being free to move around. Gel batteries have their electrolyte contained in a gel (usually silicon based) and are definitely not appropriate for this application.

I've never had an issue with venting in any of the (5) FLA batteries in my boat. If you don't need a true deep cycle house bank and don't want to have to deal with keeping an eye on your electrolyte level then AGM would be a viable (and slightly more expensive) alternative. Just match or exceed the MCA or CCA values on the battery and you should be fine.

[kurz]

Mercury OB NEVER goes up to 15V as long the regulator is ok.

[dlandersson]

Ditto

Personally I’m in favor of a dual battery arrangement with use/charge isolation switches and either a positive post or circuit breaker to be incorporated. The fuse or circuit breaker will help mitigate the risk of a deal short of the power leads between the battery(ies) and the engine (should those leads ever become compromised (pinched, fretted, etc…).

[Be Free]

Mercury OB NEVER goes up to 15V as long the regulator is ok.

We are in 100% agreement. It's not supposed to go above above 14.5V.

[macowneril2015]

Mercury OB NEVER goes up to 15V as long the regulator is ok.

We are in 100% agreement. It's not supposed to go above above 14.5V.

I will test to confirm but this is what my gut was telling me, I have battery voltage on my vesselview page and it never gets the system above 15V so I feel better now especially after what I spent on the batteries.

[Be Free]

Does VesselView give access to historical voltage data? That would be handy.

[kurz]

Does VesselView give access to historical voltage data? That would be handy.

But have in mind that the voltage at the outboard display is justan information in which direction the voltage goes. For exact data you need a multi meter...

[Be Free]

Kurtz,
I don't understand what you are saying. Please explain.
Thanks

[kurz]

The smartcraft display of my mercury 60hp (2011) shows volts. But it is not very exact. If you want to know the volts exactely, please go with a mulitmeter.

Better?

[Be Free]

That makes sense. I think accuracy to the 1/10th of a volt is close enough for his battery question.

[OverEasy]

Way more sophisticated than what our color coded charge indicator gives us
Actually ours has enough bars to be useful as each bar is measured (yes, via a ‘real’ meter) at 0.2 volts each… it flashes (Warning Will Robinson! Warning Will Robinson! ) above 15.1 volts. Serves the purpose for us as an easily checked and understood ‘at a glance’ indicator .