I beg to differ. You can over pressurize your water pump if it is of the
common Jabsco type.. These are positive displacement and the vanes block the
passage and pressurize the pump casing seals.. Seen it happen..

Although the full water jacket may not become pressurized anything between
the hose fitting and the water pump will, until the engine is started and
drawing a suction on the hose. In the Volvo MD series engines with a MS
reverse gear the raw water goes to the thrust bearing housing before it gets
to the water pump.. On other engines there could be other components. Not a
good idea to presurize system components that are designed for suction or
negative pressure.


--
My opinion and experience. FWIW

Steve
s/v Good Intentions