An electromagnetic speedometer for a boat having hull containing an opening includes an electromagnetic coil supported by the hull for establishing an electromagnetic field in the water adjacent the hull opening. A plurality of electrodes are supported by an arrangement that both closes the hull opening and supports the electrodes in engagement with the water adjacent the hull opening. The electrodes are connected by conductors with a velocity measuring circuit arranged above the hull interior surface. Preferably, the electrode support arrangement includes guide tubes supporting the electrodes for removal relative to the boat hull, thereby to permit cleaning of the electrodes. The guide tubes are closed by valves when the electrodes are removed from the assembly. In one embodiment, the electromagnetic coil is of the end-fired type, and in another embodiment, the electromagnetic coil is annular and is arranged above and below the hull.

A flow of air induces vibration of a tip of an airflow sensor. A cantilever coupled to the tip vibrates as the tip is displaced, and a piezoelectric element associated with the cantilever generates an electrical signal in response to mechanical stress or strain induced by vibration of the cantilever. A control element that is in communication with the piezoelectric element of the cantilever receives the electrical signal and derives at least one parameter indicative of the flow of air sensed by the sensor. The control element communicates or otherwise transmits an output signal that is indicative of the parameter to an output device to display sensor data to a user as desired.