Does anyone know how to increase the HP on a Johnson 8 horse motor?
Getting more power out of any motor involves:
a) making sure it's working normally (no bad plug wires, clogged injectors/carb needles, proper cooling, etc.)
b) burning the fuel more effectively (increase the compression)
c) getting the fuel/air mixture to flow better (bigger carb, freeflowing filter, etc.)
d) changing the power curve (swapping camshafts)
For the average person, apart from item a, these options aren't practical and it's just easier to buy a bigger motor.