Any idea when BIA started rating at the prop shaft instead of flywheel, and why the decided to do so ? I ask because I have a 1976 evenrude on another boat and wonder if it is basically getting the same power to the prop / propulsion
Im pretty sure it was 1985 give or take a year when they started rating hp at the prop instead of at the flywheel.... Example...a 1981 25hp evinrude would be a 20hp motor had they rated the hp at the prop in 1981 instead of the flywheel.. Not sure of the difference in bigger hp motors but any 20 to 35hp pre 85 is actually 5hp less than its rated hp as they produce more power from the flywheel than the prop... Why they ever rated them from the flywheel is beyond me....makea no sense but maybe someone with more know can chime in..
Id assume the bigger the motor the more hp is loss at the prop as apposed to the flywheel rating...id guess a 100hp fly rated would be like an 80-85hp at the prop but could ve way wrong...i just know bout the 20-35's
