The speed of a 4-punch 8-horse outboard engine depends on the size and weight of the hull, usually between 5 and 15 knots, about 6 to 17 MPH. However, many other factors, such as sea conditions, wind speed, water depth, fuel quality, and engine conditions, can also affect the final speed. It is also important to note that operation beyond the rated power of the outboard engine can lead to engine failure and accidents, so it is necessary to drive carefully and follow all safety regulations.