The 1.5HP rating is the mechanical output power of the motor, not the input electrical power. The way these motors are specified is that they put out rated power at rated current and frequency when consuming the full-load amps. Your naive current calculation fails to take into account motor efficiency and power factor. In other words, the real calculation goes like this:
V * I = P / (eff * PF)
Where V is the operating voltage, I is the current, P is the rated output power, eff is efficiency, and PF is power factor. If you solve that equation for I, that is your expected current. But there is no need to go through the math, because the full load current is already listed on the nameplate as 9.2A. So if everything is working right, and the motor is putting out 1.5 HP, you would expect to see 9.2A.
Still, even though your expectation of 6 or 7A is wrong, it sounds like the motor is consuming more than the full-load current. It is unclear from your post whether this is something new, or if it has been doing this ever since it was installed.
I can think of three reasons you would draw more than rated full-load amps. Reason one is that the pump is running at a higher flow rate and lower pressure than it was designed for. (It may be counter-intuitive, but centrifugal pumps and blowers consume MORE power when there is less back pressure... they consume the least power when the back pressure is highest in the no-flow condition).
The second reason is that something is faulty either in the pump or the motor. Maybe the pump shaft is rotating in the wrong direction or a bearing has worn out.
The third reason is that the voltage is too high and the motor is simply being over-driven.
If you have the make and model of the pump, and know the total vertical head that the pump is working against, we could maybe narrow it down a bit more by comparing your operating pressure against charts in the pump datasheet. It would be good to know if the voltage was 250 at the time you measured the current.