First time running dual alts.... Major voltage drop

[Ferguson621]

So it's my first time running dual alts, vehicle is a 2001 Silverado 1500 with the 5.3l...... right now I'm just running two ad244 220 amp alts until I come across a couple used 300+ hairpin at a good price.

 

 

I've got a 750 cca marine agm under the hood. So my issue is that now when I start it the motor lopes and the voltage drops to 9.5, the lowest has been 8.8v..... I have a power wire going from both of them to the battery, and I wired a diode going from the plug to a switched 12v source. 

 

Have I done anything wrong? 

 

 

 

Yes I've tried searching, but the oh so wonderful google doesn't pull up shit except those retarded sites trying to tell you to take it to a fucking shop.....