| Dan, Amps go up with resistance to turning, as you would see if you increased voltage for more rpms and the water medium is offering increased resistance. DC motor's rpm is voltage dependent, meaning if a motor has a winding configuration to give 50 rpm per volt, as long as the load is such to allow a given rpm, then that rpm is strictly voltage related. If you run too much pitch, the amps climb to try and get the motor to the rpm the voltage is calling for. Because a motor can produce its rated torque at just 1 rpm, they are ideal for docking. Motors are rated at both a peak amp and continuous amp rating. Say you require 10 hp continuous and your motor is rated for 150 amp continuous, there are different ways to get your 10 hp of work. If running at 48 volts you would be at the amp limit for getting 10 hp from your motor, but say your running at 72 volts, then 10 hp would only require 104 amps. You work your prop pitch (or gearing) to design a system that works for you, but as is always true in a water medium, a large, slow turning prop is most efficient. Bob --- On Sun, 10/28/12, dan.randolph <danlrandolph@gmail.com> wrote:
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