Engine worked great the first time and only this time. Sufficient power is required, as expected (requires up to 1A at 4.5V when pumping water, or less than 0.3A when there is no liquid). There was no more liquid (water) in it after the first use, when I tried to use it after a few days it wouldn't start. The reason was pretty obvious but surprising - the motor shaft was blocked by rust on the motor bearings, see pictures! Refund, apparently they used cheap material in a place exposed to water.