What is the proper size battery for my 150HP Mercury Outboard. I have 2 batteries onboard and run normal electronics (GPS/Fishfinder, Radar, VHF, Stereo)?

What brands of standard batteries does everyone reccomend?

Is your Mercury an OptiMax?, if so, they need an MCA or CCA of 1000. Even with that said, I've used and have been using a 650 A battery with no problems and have used 650 A batteries in the 150-HP Mercury I had used before repowering. Right now the OptiMax has a Marine battery I got from Wal-Mart along with a 2nd battery I got from West Marine on sale, Boaters World sells Exide's and in my boat it came with 2 1000 CCA batteries that are Interstates.

I use two Group 27 AGM batteries. Manufactured by Lifeline. I gave up on lead acid batteries in boats.

I run 2 exides in mine. Have been good to me so far.......

I use 2 batteries one for starting it's a 750 CCA and one for electronics after it's started that one's a deep cycle.