Replacing batteries on a Marlin 300

[TW59]

I recently purchased a 2012 Marlin 300 with a pair of 2011 Yamaha 300's. I recently found out that all 4 of my batteries are Interstate lead acid cranking batteries and want to replace them to have more endurance to power electronics when I'm on the hook for an extended period of time. I'm considering going the AGM route. What recommendations might you have ?

 

[Fishtales]

GW uses group 27 starting batteries. I don't have a strong idea one way or the other. Part of me says stick with what you have if new up to couple years old. Swap in pairs in different years to give you overlap. The biggest thing is to ensure the battery switches are off on the hook and run your engines long enough to charge when on the water.

 

[Fixit]

how old are the batteries? id be inclined to ride it out if batteries are still ok condition. but if your set on having agms then get two starting batteries and then as many as you can fit for the house deep cycles. I managed to fit 5 group 31 batteries in my 270. two starts and three deep cycles. I also removed the diode blocks and installed argofet solid state charging isolators and some new switches to round things off.

 

[Fishtales]

GW recommends one bank (2 batteries) for each outboard, I believe that is why they use starting batteries in addition to redundant banks. There really isn't much DC electronic equipment on the GW anyway. If you really want to have a house battery, it would be a lot of work but you could add a 5th and let the wiring begin. I'd just keep what you have at this point. Just my 2 pennies.

 

[drbatts]

Not sure if Yamaha recommends using AGM batteries. Assuming you marlin battery setup is similar to my express, with 2 banks of 2 batteries in parallel. Other options would be, to replace the house bank with 2 deep cycles which should meet yamahas power requirements and be a better house bank then 2 starting batteries, and the other bank with 2 dual purpose batteries. This would be a straight up replacement, with no wireing changes. Or you could with some minor wiring changes give yourself a house bank with 2 deep cycle batteries, then have a single starting battery for each engine.

 

[seasick]

Check that your engines are compatible with AGMs.
Also check that your engines are OK with deep cycle batteries versus starting types. Not all engines are. Some models of starting AGM batteries(like Optima Blue) specify that they should not be used as deep cycle batteries for constant loads,
Note that running starting batteries and deep discharging them is not healthy for starting types and deep discharging can reduce battery life.
At the same time subjecting deep cycle type to heavy starting currents can also reduce the life or damage the cells.
So the simple answer is just swapping in different types of batteries is not a good solution. Evaluate your power needs realistically and maybe all is OK as is.
If you want/need to add specific house batteries for accessory loads, you need to add separate charging leads and isolation.
Adding an ACR may help reduce the chance of running down your starting batteries.
Also remember that batteries in a parallel wired non isolated bank should be the same type, brand, and age.

 

[Hookup1]

I have 4 separate batteries on my boat. 2 starting, 1 house and one for bow thruster/windlass and bait tank pumps. Charging shunts on both engines to charge the other two batteries. All Duracell AGM's from Sam's Club (best price). 3 - 34M's and 1-27M. I never shut my engines down. Yamaha alternator keeps them charged even at idle. Never get a low battery warning. If you switch to AGM's make sure your battery charger can support AGM profile.

 

[eppem]

Call Grady? They will tell you exactly how the boat left the factory.

 

[SkunkBoat]

I split my batteries out so that I have one starting battery for each motor and a House pair of DC that is separate from the starting batteries. The house charges separately using the Aux charging cables(yamaha has these available). Both motors charge the House. The House does not drain either starting battery.
I can drift overnight in the canyon, no generator, motors off, run deck light, uw LED, sonar, chart, VHF, Navlight

I stuck with flooded Lead Acid. I don't see any upside to AGM for this purpose.

here is a link to what I did to give you an idea of what can be done.
https://www.greatgrady.com/threads/new-battery-config-for-265.25744/

 

[mikesne]

Hi,
I just spent too many hours to count researching boat batteries. There are pros and cons to each type and each has special capabilities and or limitations. Lead acid can only use 50% of the rated amp hours and diminish after each cycle. AGM are somewhat better, both are suitable for starting power and some are rated for deep cycle and starting. I'm in the process of purchasing lithium batteries for my house batteries, they can be discharged, and recharged 100% and have a 10+ year lifespan. They require a special charger and can be damaged by charging with the motor alternator. You may also want to consider an automatic charging relay (Blue Sea systems), this separates your house and starting batteries, thus never leaving you in a situation where every battery is dead.

I urge you to watch Jeff Cote's Pacific yacht systems video's on Youtube. This guy is an electrical engineer who does nothing but boat electrical, he is amazing.

 

[DennisG01]

I was going to start from scratch with my response... but I'll just reiterate/add-on to some of the things that Skunk said as that is exactly the way I would go. One starting battery for each engine and then a SEPARATE bank (which can one or two batteries) for the house using deep cycle batteries.

Use at least group 27 for the DC, if not 19 or 31 to get maximum time without the engine on.

AGM vs Lead Acid shouldn't really be a problem as the charging profiles are close enough. Gel batteries are the ones that are different.

Not sure exactly what your battery and switch setup is, but... you could easily setup each engine to be able to start via either starting battery using (2) 1-2-Both-Off switches.

 

[mikesne]

I was going to start from scratch with my response... but I'll just reiterate/add-on to some of the things that Skunk said as that is exactly the way I would go. One starting battery for each engine and then a SEPARATE bank (which can one or two batteries) for the house using deep cycle batteries.

Use at least group 27 for the DC, if not 19 or 31 to get maximum time without the engine on.

AGM vs Lead Acid shouldn't really be a problem as the charging profiles are close enough. Gel batteries are the ones that are different.

Not sure exactly what your battery and switch setup is, but... you could easily setup each engine to be able to start via either starting battery using (2) 1-2-Both-Off switches.

Or use an ACR and not need to worry about switching by hand.