Electric motors run reliably as long as they have enough power supplied to them. The question of “how good are they?” is just the incorrectly asked question “how good are the batteries?”
We have crossed the Atlantic twice and visited many ports along the way. We have managed this on just eight 100ah batteries hooked up in series and parallel to give us 200ah at 48v. As a result, we have practically no range and as a result do not count on our electric motor to take us far. We have been using it just for docking and maybe for maneuvering around an anchorage, otherwise we rely solely on the sails to get us from port to port.
After 4.5 years, we have never actually done a proper range test to see how it works. Now is the time to see what this baby battery setup can do!