Anyone using these instead of Marine deep cycle. Based on my research, seems like you should get longer run time and life span.

What does your research show?

Deep cycle is deep cycle if your comparing similar size batteries then life should be similar assuming similar care is taken.

The all time best battery I've ever run were gel filled for electric wheelchairs. Sonneshien, the US distributor is in Missouri, they aren't light, but nothing I've used was equal. Closest are oil filled Thermo's. Either are way better than the junk "marine" batteries peddled to us.

Two 6V golf cart batteries will give you a little more running time, but you have to weigh the extra capacity against the weight. Also remember, that if one goes south, you are stuck with 6V which will not get you home. That said, a properly maintained and charged true deep cycle battery should easily get you through a day of fishing.
Pat is correct about the junk batteries. I've gotten into more than one argument with the clerk at Auto Zone or Wa Mart over batteries that they are supposed to know about. The so-called marine starting or dual purpose batteries sold at Academy and Walmart are junk. The plates just will not hold up to repeated deep discharging. A true deep cycle battery will be marked as such and should give amp-hour capacity. CCA mean little here. You are buying a battery to run a trolling motor, not stat your truck. A group 24 battery will have around 85A of capacity and a group 27 around 105A.

Different battery plate construction in golf cart deep cycle wet cell battery VS. marine deep cycle wet cell battery. Golf cart battery built to withstand many more discharge/charge applications. Avg. 12-15 pounds more in weight. Have not gotten pricing yet.

They are heavy as carp,I'll say that they do make 12 volts want to say I've seen a 24 volt one but not 100%

Nope. 6 & 12V only..

If you go this way, I highly recommend the water maintainence system with them.

Roland Martin was using golf cart battery`s during a tournament some years ago and got stuck on a sand bar. Cost him a lot of money. They are too heavy.