Someone once told me sometime in the 90's the horsepower ratings changed for outboards. "The horsepower is now rated at the prop, not the power-head." Is that true? If so what's a good rule of thumb for figuring out an equivalent newer outboard vs an older outboard? Is a new 2009 50 HP equal to an 1970 50 HP or more like a 1970 70 HP? Just curious...
