What is the horsepower in a 175 cc engine?

It depends

The horsepower of an engine can be given in either brake horsepower (bhp) or shaft horsepower (shp) - they will not be the same number for the same engine.

While a higher volume engine generally corresponds with higher horsepower - all else being equal - it is not the sole factor in determining horsepower:

The horsepower depends a great deal on the compression ratio of the engine.

The horsepower depends on the fuel the engine is designed for - which is heavily intertwined with the compression ratio of the engine (a diesel engine is usually designed to employ higher compression ratio than gasoline).

The horsepower depends on whether it is a 2-stroke or 4 stroke engine (175 cc could be either).

Horsepower can be increased by engine tuning, more volatile fuel, supercharging or exhaust turbo boosting.

With all that said, a reasonable guess for the most likely 175 cc engine you might be looking at would be between 10 and 12.5 bhp.