i have a 94502mpi mar.has silent choice.i belive the riser is a stock merc,cast ss.on the side of the riser is a hose bung that is capped.it is 180 degree from the outlet on the riser.can i use this port for my water dump ?

Water dump for what??????? You cannot run stock merc exhaust dry.

i ,my water pressure is highneed a dump port because i am installing a pressure relief valve.since i changed to a newer style bravo,my pressure is high,35-40 at wot.i was looking to use this port at the riser rather than drill a hole in the hull.