High capacity AAA NiMh cells are a poor choice to provide power to motors. They have a high internal resistance so are incapable of providing higher currents without a high voltage drop. They are designed to power electronics with a low current draw.
Jim
I wish somebody had told me that before I did it and found out that they work, albeit in a boat running rather less motor.
But it was a slip of the finger, should have been AA cells.
The string of 5 AAA was in a boat powered by a servo motor, duration was over 1 hour, enough to get round the 1 mile of lake side and then mess about a bit. Since replaced by a pair of 18650 Li-Ion cells in holders connected through a harness and working the boat via a 5A UBEC. The labels claim 9800 mAH. Obviously low C rating, but I haven't had the opportunity for a proper trial yet.