Thanks for the info everyone!

I have a Group 34 Blue Top. It�s for the engine, and only the engine. I have a 4-s Yamaha and it has a dual charging circuit that allows me to have two batteries, isolated, and charged from the motor. The second battery is a Group 27 Blue Top. It runs everything besides the trolling motor and the engine. ....you guessed it, I have Group 31 Boue Tops for the ultrex.

Yeah but you're prolly rich, I can only afford those cheap Walmart battery's. However both trolling motor battery's have 3/15 stamped on them and they spin that Ultrex like a top.

Currently running Durcell AGM 31. Best is North star NSB-AGM-31. Believe North star supplies Batteries Plus PowerX2.

Ya we run them on a 36 ultrex but it's not enough for the 250 plus all the accessories. The "cheapest" big dual purpose I've found is the exide megacycle 31. It'll run 4 graphs, pumps, poles, all day and still crank up 8 hours later

Nope. Just taking advantage of an Optima sponsorship from another hobby. Lol.

I'm running similar set-up with the Blue Tops in all 4 banks; 34 and 27s. Fortunately, came with the boat when purchased - them are pricey buggers.

If you have room, run another cranking battery in parallel. You will never have a problem again. I took a trolling battery and set in passenger storage box. Used that spot to run a second cranking in parallel. Workes great. Make sure to use #2 cables with heavy duty ring lugs for the parallel jumpers.

Older Mercs (EFI) not recommended to use deep cycle AGM batteries for starting batteries. I think it builds up heat and burns stators.

Here's a BBC thread on it: http://www.bbcboards.net/showthread.php?t=827947

I like King's idea if you need more reserve add the 2nd starting battery if you run wet cells.

Most group 31 AGMs are the way to go.

Nope. XS, X2 and two others are Fullriver's.
Napa/West Marine AGM's are Deka/MK/East Penn (all the same)
North Star is considered "OK" by folks in the battery business. Like Optima, their big marketing has caused people to buy the hype......

From a practical, engineering and field proven perspective, Odyssey, Lifeline and Full Throttle are easily the strongest AGM's - with warranties to prove it.
Each has a particular strength over the other, but they run neck and neck overall for a dual purpose marine battery.

Marc

Fullriver �full throttle� batteries are Chinese junk. Sorry bud.

I�ve had better luck with interstate than any of the others. Including Optima.

I would love to know where you feel they are lacking?

Years ago, I was fed the same hype about them being junk - then we started deploying them in the field after extensive testing against other brands. Our applications include pipeline cathodic protection, turbine engine start, arctic telemetry buoys, remote surveillance equipment in Alaska and and our southern deserts.
Between Concorde and Fullriver, we deploy 2,000 to 2,500 batteries per year. We are seeing an extremely low failure rate spanning many years of rough duty. When our systems fail, we get a black eye.

Your applications may be very different, but my experience has been very positive!

Marc

Interesting real life fact based info. Would you say your application mimics �deep cycling�? Used for hours/days and drawn down quite a bit before being recharged? Also have the batteries been lasting years in this application? Thanks.