HP Rating at Head or Prop

notlemt58

New Member
Joined
Jan 16, 2012
Location
Manorville, NY, USA
#1
Does anyone know when Mercury began measuring hp at the prop? And, if a 150 was measured at the head (my old 1985) what kind of increased hp would a modern day 150 give me compared to the old. Ex: If mine was at the head, is it the same as a 135 at the prop, or more or less?