Check these out.

http://www.odysseybattery.com/marine_battery_specs.aspx

He's gonna be running a 20 foot boat with duals, so i can almost guarantee there will be less than a half mile an hour difference between the lithium andl lead/agm. If you wanted to go really light you could just buy the 24 volt lithium battery from lithium pros. And only run the one battery. It has more than enough for the two motors. http://lithiumpros.com/product-category ... es-marine/

If the guy is doing well enough to even consider 4000k worth of batteries, he's doing well enough to make this mistake over 50#s and 0.0001 mph slower.

thank You guys for all your answers. I have talked to Bubba from GT and he says the GTR37EFI needs a 230CA battery as a mininum, I am looking at all the options.

I like those Shorai batteries, they are very light and have good juice, after I use the boat I can just connect the BMS01 charger and leave it on indefinitely. Hell they are so small and light I can buy 3 and have a spare one on board, all the 3 batteries will weight 15 pounds in total, they have a very good Price too.

Man your boat won't even notice 2 big batteries are even in the boat.

I would say you are over thinking the battery a weight issue. I currently have a 430 cca battery and it can struggle at times turning over my modded 23. I plan to step up to a optima with 800 cca and more reserve capacity for running my lights while setting decoys. I rather have more than enough juice especially way back in the swamp. 40lbs of extra battery weight won't equate to any real change in speed

I will have My Twin engines stock and the manufacturer is saying I need 240CA, those Shorai have 540CCA which is almost 650CA and 36A/H. The led Rigid Industries lights I Will install draw around 17amps plus the interior leds, with Two Of those Shorai I could have My engines off and have enough juice for all My accessories for more almost 2 hours and they are $200 each. What is the problem with those Shorai batteries? Why wouldn't they work? As I said, they are so small and light I could have a third one as spare. I am listening to all your suggestions and I really appreciate your help but could someone please explain what the problem with those batteries could be?

Most of us just don't tend to spend over 300 bucks on a battery. With what I know of charging lithiums, I don't trust the Briggs charging system to regulate consistently and correctly to not wind up destroying a lithium. But with further research, or someone more knowledgeable, I could very easily be proven wrong. I do know it behaves fine with lead acid and agm. So there's that, for what it's worth.

No one way in hell I'm hooking up an optima to a small engine. The only experience/research I've ever seen says old school lead acid batteries or big deep cycle batteries g27+ work fine on small motors, I don't understand hooking up a $200+ battery to a lawn mower motor and hoping you get the same performance as an offshore boat/outboard. Much less a LiO nexgen battery

Pretty sure most of MMT is humusexshuls in hiding

Jayhawk your an idiot. I ran an optima battery on my last rig. Was one hell of a battery. No one expects there battery to improve performance . My purpose of my optima battery is the other batteries were too big to fit under my back deck. I wanted to keep the battery out of the way. I had the optima in my boat for 2 years and had no issues. The Briggs charged the battery just fine but that's just my personal experience.

With the 50amp x 2 charging system you could use one regular battery if your cutting weight.

scroll down like to half page and read where it says "marine" FAQs

http://lithiumpros.com/support/faqs-2/

lots of reasons why go with a Lithium battery

There's a lot of info there that doesn't do anything to confirm these Briggs charging systems won't over charge or damage the lithium. So yeah, let me know how they hold up. I'm good with paying less and living with a 47lb battery.

No. 20 at idle, I believe (could be wrong here), then 50 once you get over somewhere around 2200 or something (I don't know exactly). The non cdi (older engines) were 20 amp at 2500 or something, and nothing below that.

My brother has good luck with both trolling motor batteries and cranking batteries. But what he does is charges once a week, no matter if he is going out in the boat or not. So for him to get 5 or 6 years is amazing to me but he says the charging helps. He just gets Exide batteries when they go on sale at Academy.

if a Battery is 540CCA, any idea how many CA would that be? I believe close to 650CA, is that correct?

Thank You