Three generally parallel curves started at the lower left and rose to the upper right. Outboards were on top, followed by 4 stokes or high output automotive engines and stern drives were the bottom curve. I requested a copy of the graphic. He said he would ask for clearance to send us one.
Stern drives are lower cost.
Outboards have a higher horsepower per pound ratio. The new marine engine paradigm. Agencies have forced a rationing effect on outboard emissions by year. They are moving from carbureted engines to EFI and then to more DFI engines. In California you are awarded one to three stars to put on your engine depending on which standards it meets.