NEEDS CABLE THE MOUNTS DO NOT MAKE GOOD GROUNDS.

As said before, without a good low restrictive ground the system will seek any ground it can find. Through the drives, harnesses, etc. Put it on you need it.

If you had one bad ground it's time to clean all the connections. If you put a ground cable between the batteries and between the motors it'll be good insurance and provide more voltage to either starter while cranking. The extra ground paths will reduce the cable resistance, increasing cranking voltage at the starters.

Thanks all, I removed the stud on the back of the motor and cleaned it up with a dremmel. I also coated the stud and connectors with a die electric grease that you use for electrical connections. I will remove the other stud and do the same. I also bought a long ground cable that I will put between the studs.