"Here's what (little&#
"Here's what (little) I know:
The Yamaha designed Merc engine series consists of a family of engines designed about a 20 cubic inch cylinder. To wit:
Two cylinder motors (40 cube) are 30 and 40 hp. The 40 hp engine (20 hp per cylinder) is de-tuned with (probably a smaller carb, tighter tuner, and possibly milder porting) to make a 30 hp motor (15 hp per cylinder). It's easier that way.
Three cylinder motors (60 cubes) run from 40 to 60 hp. The 40 hp version (note that it's also 15 hp per cylinder) is the de-tuned version of the 60 hp (again, 20 hp per cylinder).
The 90 hp is a larger engine (85 cubes) is already at its max, with de-tuned versions of 75 hp, so you're out of luck.
Jeff"