Small outboards: 20-25 HP = 15-30 mph (0.8-1.3 mph/HP) Average cars: 65-300 HP = 70-170 mph (0.6-1.1 mph/HP) Large motorcycles: 55-220 HP = 90-170 mph (0.8-1.6 mph/HP) UTVs: 50-170 HP = 50-85 mph (1-1.2 mph/HP)