Dual Battery Selection

[Juttmk]

23' Mariah Open Bow
7.4L
Dual battery 1-2-All
Just purchased the boat and need some recommendations on battery selection. Battery 1 is currently wired for starting only. The 2nd battery is wired to run the led lights, subs, and other accessories throughout the boat. What are your thoughts on going with (2) Group 34M AGM Duracell batteries? I figured I could start the boat in the "ALL" position and once we stop to in the cove selector switch could then be moved to battery 2 for the Stereo and lights. Thanks in advance!!

 

[bruceb58]

Or get one of these instead of the 1/2 both switch.
https://www.bluesea.com/products/7650/Add-A-Battery_Kit_-_120A

The ACR charges both batteries while you are running.

 

[JASinIL2006]

+1 on the Blue Sea Add-A-Battery kit.

 

[Silvertip]

Hmmmm! The OP asked for battery type suggestions and is told what dual battery system he should switch to. With that in mind, buy whatever you want until your wallet objects. I personally do not feel it is necessary to spend big bucks on so called, high tech batteries, especially AGM's but that's just me. A pair of group 34's is probably overkill, especially on the starting battery. Both batteries do not need to be the same size. You also don't need to start the engine on BOTH. Start on any setting as the little bit of current that's used to start a properly tuned engine is quickly replaced anyway.

 

[km1125]

A pair of group 34's is probably overkill,

I was actually thinking that the group 34's were probably under capacity for a 7.4L starting requirements. What the MCA minimum for that motor?

To the OP: If you're looking for the best mix then you should have one starting battery and one deep cycle if you're going to use it as you describe. Whether you upgrade the switch to the Blue-sea system is a different matter, but it is much more convenient and you don't risk 'forgetting' to decouple the batteries when you are on the hook.

I'm not big on the expense of AGMs either.

 

[dingbat]

I was actually thinking that the group 34's were probably under capacity for a 7.4L starting requirements. What the MCA minimum for that motor?

Mercruiser list it anywhere from 575 to 850 MCA depending on the configuration.

 

[bruceb58]

I have 2 AGMs on my Wellcraft and will replace them with AGMs when they die. I think they are a great choice and well worth the money.

 

[JoLin]

I have 2 AGMs on my Wellcraft and will replace them with AGMs when they die. I think they are a great choice and well worth the money.

The PO of my boat installed AGM's in 2011 and (knock wood) they're still going strong. However, these are Lifeline brand batteries and pretty pricey. I'll have to see what my wallet looks like when they die. Thing is, unless you maintain the batts properly (keep 'em charged and don't run 'em down too much between charges), buying AGM's won't pay off.

My .02