There is not such conversion of displacement to HP. You have what is basically a 17 cu. in engine and that would seem to be and 8 to 10 HP engine in an OHV configuration.
7 to 8 hp
9.5 h.p.
About 7-9 horsepower.
There is no standard relation between horsepower and engine displacement.
12 hp
CC is NOT correlated to Horsepower. Cc is merely the capacity of that engine, NO relationship to horsepower.
You are going to use it in a lawnmoer to race they are i think about 15 hp but if u want a fast lawnmower use a snowmobile engine
1 cc = 0.0338140227 US fluid ounces144 cc = 4.86921927 US fluid ounces