Which Optimas are most popular for 36V trolling motor

I use the D31M Optimas, p/n 8052-161, purchased from Street Side Auto, www.streetsideauto.com
Best price I have found, just replaced all three of mine. Free shipping too.

I use the blue cap 31 series as well. I do not get mine from streetside though.
Amazon is cheaper

Amazon is a little cheaper but in reading on-line reviews, I noticed some folks were having warranty issues. Street Side is an authorized Optima dealer, not sure if Amazon is. I just felt more comfortable with Street Side. No shipping or tax helped.

I'm convinced that many if not most optima batteries dont have the original code date on them. I believe they over produced and demand was so low that they (or the retailers) put new labels on old batteries.
I don't think there's anything wrong with them doing that since they honor the warranty. But it is misleading and u may buy a 5 year old battery with a new code.
I got one in May with a code of D6 (April 2016) that looked like it had 5 years of dust on it.

In the past, they would last me up to 5 years. I haven't had one last 3 years in a long time.

They have a 18 month warranty. If i can get 18 months out of them, i believe i got my money's worth. But most people expect longer life. Im very hard on batteries!

Ive seen 4-year-old gel batteries on the shelf at Academy. Consider the possibility that u may need to redeem warranty

Do some research before you spend the money on Optimas. There have been at least 3 folks here of late that have purchased Optima Blue tops that were bad from the get-go.

I've owned a bunch of them IMO you should just plan to replace all marine batteries after two years.

+1 ON STREETSIDEAUTO. GOT MINE THERE DEFIANTLY BEST PRICE YOU CAN FIND. $175 TO MY DOOR FOR D34 THAT I AM USING FOR THE CRANKING BATTERY AND ABSOLUTELY NO PROBLEMS. WAS HAVING PROBLEM WITH GRAPHS SHUTTING OFF AND HAD TO USE CROSS OVER SWITCH LAST WINTER TO CRANK MOTOR. NO PROBLEMS NOW SINCE INSTALLING OPTIMA.

COOL STORY BRO

you MUST have a proper charger for Optima's otherwise you will kill them is a couple of years.

i installed blue tops in one of my previous boats and had to replace every one of them with in 6 months of purchase. I have 2010 everstarts in my boat right now and they held up to a 13hr night tournament last night. Im about to replace my batteries just for piece of mind and I am about dead set on just going with everstarts again. the price is hard to beat and if one goes out your never very far from a walmart.

It's all in how you charge your batteries... I just replaced my dekas with blue top Optimas... Got 3 years outta my dekas... Not sure how long they been on the boat before I bought it... Dekas are great as far as I'm concerned... I'll let you know about the optimas in a year or two...

Been buying blue tops for 10-12 years now, and have never had a single issue with any of them. I am going to continue buying them until I guess I start having problems. Guess I have been lucky.

My Optima Blue tops gave me 5 years of service. Made sure to charge them every week, fishing or not. In my opinion, that's the key.

That and never letting them get down too low or close to zero charge.