Sounds like your timing is way off not a batt or starter and thats why it will not idle
Sent from my SGH-T999 using SoCalJetBoats mobile app
Basically when I had one battery hooked up it didn't have enough cranking power to start it but when I hooked up the second battery it cranked fine a friend of my dads said it was because the cam was at TDC and in just needed more cranking power to spin it
And this. Could be something as simple as a junk battery. I've run single batteries has high as 13:1 compression, or 9:1 compression and blown and never heard of this! Chris (88Carrera) should be able to help you diagnose this easily enough.
Could be cam timing is way off, but I kinda doubt that unless the timing set is junk. This would explain the idle condition as well, maybe. dunno.
Personally, I'd be looking at a junk battery and a junk throttle cable as the probable cause for 99% of your issues. Rest assured, it's almost ALWAYS the simple chit that we overlook..........

Ray