The impeller should go 16’3” from the bow. If elsewhere on the boat, the SpeedCoach should be recalibrated. It should be positioned approximately under the footstretchers. While the impeller does not need to be on the centerline, it must be submerged (if NOT centered be sure to still align the sensor accordingly with the movement of the boat). The impeller can be adhered to the hull of the boat with double-sided tape (included with purchase) or good electrical tape.
The SpeedSensor, which is the blue sensor provided, should be as close to the impeller as possible (maximum or 11”). You install the SpeedSensor inside the hull (i.e. the opposite side from the impeller). The SpeedSensor can either be installed perpendicular to the impeller when positioned directly above it, or parallel to the impeller when it is located one impeller length in front or behind of the actual impeller. Although inside the hull, the SpeedSensor still must be fixed securely to the shell. Make sure you clean the surface well before taping it to the boat.