Weaver,
I don't use 3/16" 7018 often anymore, but as memory serves, I would have said 175-200 for any position depending upon material grade, thickness, and position.
I have used 3/16 in the overhead mainly for fillets. Doesn't do too bad when running in the sweet spot for amps and, depending on Miller or Lincoln, options for arc characteristics.
Down flat on heavy material you could probably get by up to 225. I haven't even looked to see what the manufacturers' recomendations are, just memory. Could be all wet.
Have a Great Day, Brent