The Spartan is a 5s boat. I run mine on 6s and 5s, its stock and it will go 48 (6s) on my GPS. The problem is the 6s voltage 24 volts x the motor KV 1800 , this puts the rpm at 39960. over what it should be by about 5000 rpm.
hence the boat will heat up on 6s. You have to manage the throttle on 6s. The flex cable will auger the grease out of the liner every run so you have to grease it after every run.

Compaired to my Aquacraft UL-1 hydro that is 4s and goes 40 out of the box. I got a metal prop for it, taught myself how to sharped it and I have it on gps from 65-68 mph, running 4s.
I grease it once and run it 10x. Hydro's are designed to turn RIGHT by the way.