Mtroniks Viper Marine 40The Viper Marine40 is a brushed speed control designed specifically for use in RC model boats. It has a 40Amp motor limit, what this means is that you can use any, DC brushed motor, as long as the current drawn by that motor does not exceed 40Amps under load (with the prop connected, under water). The Marine40 is the perfect speed controller for anybody wanting to either upgrade their old speed controller for a no nonsense 40Amp limit reversible