Low Amp Draw on 5kW Outboard

[GrandeDan]

Hello all,

I am trying to make a homemade outboard with the 5kW motor. The trouble I am having is when I am under way, my max amperage is set to 93 amps but I only reach 77 amps at full throttle. My max RPM's is set to 4500 but I only reach 4000. I am using an appropriate 48v battery that has been used to draw far more than 73 amps. Any suggestions on if I have a setting on my controller wrong or why I wouldn't be receiving the full power I am asking for?

[Bikemad]

Hi andto the forum.

The HPM48-5000 motor produces its rated 5kW power at or below its rated speed of 3,500 rpm. Above this speed the current draw will drop considerably as it approaches it maximum unloaded speed of ~4,390 rpm.
According to the dynamometer data, if the motor is loaded sufficiently to keep its speed below 3,500 rpm at full throttle (with a suitable controller and battery setup) the current draw would be well in excess of 130 Amps. 

Therefore, assuming that my calculations are correct, you would need a larger diameter prop (and/or a larger pitch prop) that would place enough load on the motor to keep its rpm below 3,688 rpm in order to draw the maximum 93 Amps of current that you have set on your controller.

Alan