We run our Webasto on 50 and 60 hz and it works fine. Probably some reduced efficiency at 50, but we don't notice. You need to make sure the
pump is rated for 50 and 60 as well. Our
boat is 240 so we need no step down transformer. Just
plug and go in 240/60 or 220/50. All consumers wired to
shore power or genset can take either. Of course, there is an
inverter or a
single leg for everything else (which is just wash machine and outlets).