In Bluetop, all I'm seeing is dual purpose batteries. Is this correct? Which model do you use?

I love the Optima D31M as my starting battery, but I won't be going Optima for TM as there are other options with more reserve minutes (or AH rating) for less money. WHen it comes to reserve minutes (which is king for TM run time), Optima is not the king of the hill.

The Optima choices for all things on boats are blue, Blue, and BLUE. Pick any one of those you want, but the brand doesn't mean it stores more energy - that's determined by the Reserve Minutes. Optima batteries lack a bit on that spec compared to some other choices because their product is dual purpose, which penalizes the deep cycle performance somewhat compared to those other choices.

But do the other choices with more reserve minutes last 4-5 years on average, like the Blue Tops? If not, the Optimas may still be less expensive in the long run.

ODYESSEY

You are correct. Note I did say "some other choices" without being specific. I'm not hard-set on just one right answer. There are multiple good ones available; some of those will rival blue tops in one way (deep cycle use) but not another (such as dual purpose use - i.e., starting/electronics).

Is not the Yellow Top what they consider a deep cycle battery? In years past I thought the Yellow Top was dual purpose and the Blue Top was the deep cycle. Did something change?

Yellow Top has never been a marine product line to my knowledge. The Yellow Top is a severe-use automotive product for vehicles that have more than normal drain other than starting. (Think winches, optional lighting, high power stereo systems, etc. in addition to starting the vehicle) They cost more than red top - where red top is the standard auto product line.

Ok, but I don't think that there is a difference in the batteries.....I'm looking at specs and battery for battery they look to be exactly the same. Both show to be a dual purpose type battery. I think it is a marketing ploy. The specs are pretty much identical. Price wise the Blue Top is more which is why I'm wondering about the differences. I'm thinking about the Yellow Top as my new starting battery and to run the electronics.

They tout that the marine batteries have been reinforced to withstand the rigors of being on the water. That alone could be the difference between Yellow and Blue - where the additional cost is to cover the more robust mechanical design (such as thicker case wall, and spacers to insure plates never contact due to a rough ride).

How much do you save over the D31M? That's the sweet blue top for a main battery. If the Yellow is less, but fails due to severe vibration (compared to automotive use) or doesn't last as long, do you really save?

According to a major parts house its about a $60 savings but IF the difference in Yellow and Blue are in fact construction for Marine application, then yes, it would be worth it.

Just for giggles, I sent them an email to tell me WHAT the difference is between them. On the spec sheets they are the same battery. If there is a physical difference that makes the Blue better for marine applications then I would love to know what it is.

So which deep Cycle battery is the best value if it isn't optima? Not buying a 300 dollar battery

I don't think Optima yellow top batteries have the extra set of threaded posts that a typical marine battery has. Optima's spiral cell design is sort of space inefficient compared to a regular battery, so there is less room for lead and electrolyte inside. Because of this, an Optima battery will be a bit lighter than other AGM batteries of the same size and have less capacity.

Please post with info after you get a reply. I would like to hear what they say too!

Very good point on the threaded posts. They're stainless steel on marine batteries, too. I gotta have that for reliability/security of the connection.