Aight, 36v trolling motor. Pretty sure 1 bat is dead and gone. Question is, do i need to replace with the same size battery? The 3 in boat are 31m. Would going with a 27m be a no go? Diff in price is about $140.

You won't have near the amp hours with a 27 as a 31. Also if your other 2 31's are weak, they're gonna pull your new battery down. I think most people recommend replacing them all but I know there's folks that don't.

$800 to replace all at same time 😳.

I agree. It’s going to suck but I would replace all three. And also check your date codes on the new batteries you are buying. May want to check the the codes on your current one as well.

If one is dead, the others will probably die soon. If you have any other sort of marine battery you could replace the bad one on a temporary basis, and run it until the others start giving you trouble. I wouldn't buy a new $250 battery and put it in the string with 2 that are old. The old ones will drag the new one down before it's time, and you will constantly be replacing batteries.

If I didn't have a lot of funds, I would consider buying 3 group 31 batteries from somewhere like Advance Auto. Use their discounts, and you can probably get them for $300. I've had good luck with them and use them on my boat.

DON'T go to a lower battery amp/hr rating. If your using a minnkota 112lb trolling motor then its drawing around 52 amps and your gonna need at least 3 batteries that have a minimum of 105 amp/hrs if you plan on fishing all day or in heavy wind. If your fishing current for an extended length of time your gonna want 3 batteries with 120+ amp/hrs. If you have been using the 31's and been happy then keep using them but don't go to the 27. You will not be happy. The 27 has about 80 amp/hrs vs the 31's 100 amp/hrs (approximation depending on battery name brand).

What kind of batteries are you running that costed $800 for 3??

Had in my mind they were 249...

With that price, you are nearing an Absorbed Glass Mat replacement.
I converted one of my trucks already to AGM.

31 series odyssey extremes. Worth every penny

If you are gonna buy from Advance, put it in your shopping cart and then don't check out. They will soon be emailing you offers for at least 20% off; maybe more. I bought the last group 29 I got from them for around $70, but it didn't have the diehard name on it.

Good idea preacher.

Thanks pcp! And i dont need the diehard name either.

Goan, check your PMs

gman go check at Craigs across the Beltine from Krogers.

Deka Group 31 run me $140 each and they have been good in my boat. If the existing batteries have nay age on them replace all 3.

Sam's Club sells Duracell brand which I understand are Deka. Group 31 AGM are $180.

Yeah, but we ain't a member and I'd have to drive to hsv. Craigs in decatur or my local advance with my "speed perks" is prolly gonna be how i go.