Impossible to say without more details. There's a lot more to horsepower than just size. Single or multi cylinders, 2 cycle or 4 cycle, level of sophistication, all have a bearing. The 180cc engine on my power washer is not very sophisticated and makes about 12HP. An engine that size on a competition motorcycle might be capable of 35-40 HP. It also costs about ten times as much.
5 hp
No.
21.5
Displacement doesn't directly equivocate to horsepower.
8.0 horse power - 125 cc
the cubic centimeters of 6.5 horse power is 175 cc
10 horse power
It's about 5.5hp
50 horse power
you can convert cubic inches to cc's but not horse power. an engine with say 65 cc's can have different amounts of horse power depending on carberation, pistons, valves etc. etc. etc. but my 65 cc engine does have 1.89 hp if that helps.
CC can vary between 15 and 17 cc per horse power, so a 3 horsepower motor has a cc of about 48 cc.
148 cc is 3.5