A flow measuring system is adapted to measure flow in a sub-sea well. The flow measuring system has a housing, attached over a hole in a riser creating a fluid pathway therebetween. A deflector plate is attached to the riser and covering some of the hole. Upper vertical louvers and lower vertical louvers directly attached to the deflector plate over the hole. Apertures in the upper vertical louvers and the lower vertical louvers permit fluid to flow through. A flow measurement device is mechanically coupled to the housing and the deflector plate and configured to determine a speed and direction of flow through the fluid pathway.