I've got a Mercury 30hp 4 stroke that has a carb'd 3 cyl Yamaha powerhead, it's a couple of years old. Question is: I believe this engine is detuned from 40hp since it is identical in all specs to a Merc/Yam 40 except the power rating. Anybody know what it would take to pump it back up to 40hp? Carb jets maybe?