This is a battery question, how would it not have something to do with it?

An 1/8th scale hull takes a high amount of power. Running 3 - 3s packs in parallel would not do much for it. Running 3 - 3s packs in series would get the voltage up where it needs to be. However the batteries must supply the amount of current demanded.

It is absolutely critical to make certain there is no confusion about what each wiring method has to offer.

eboat has already explained how to wire it to achieve the proper voltage needed for a 1/8th scale.

Ryan