Most motors I have seen were rated 208/240. With respective FLA.
Motors will put out the power needed, if the pump requires 5HP the motor will put out that 5 HP wether it's a 3HP motor (it'll burn) or 10HP (will run somewhat higher than 1/2 FLA). At the same time the ampacity on an inductive load will be inverse proportional to the voltage (unlike resistive loads where the ampacity is direct proportional to voltage). So running a motor on a higher voltage will cause the ampacity to drop, how much higher voltage you can run it on depends on the insulation VS the voltage. Obviously we all know that 5KV requires much thicker insulation not because the ampacity but because the electrons on 5KV will jump through the insulation 600V don't.
So if a motor is rated strictly 240 and will be run on 208 it'll overheat IF run at max horsepower (keep in mind most times engineers oversize motors to be safe). On the other hand if it's rated strictly 208 and will be run on 240 the insulation will get compromised eventually with time.
Last, let's not forget motor designers will take in considerations voltage drops, overvoltage and overload, so technically there's a little wiggle room even if a motor is rated strictly a certain voltage.
But again, I don't think I have seen a motor rated strictly for 240 or 208.
But its a violation of 110.3(B), Mike Holt has a graphic on this, and 240 V motors are not happy on 208