So, I take it you don't want to buy my variac?
Good.
$20 was way too cheap anyway now that I looked up the specs and the list price.
Do Mag drive pumps have synchronous motors? (I've noticed that Iwaki's have substantially lower specs for 50Hz vs 60Hz operation, so I suspect they do operate synchronously.)
If not, I'd be tempted to use the variac to put 140V into my Danner Mag 5 and see what happens.