Component description RPM sensor (51.27120–0008 / –0009) 2 1 2 1 5 5 3 4 3 4 Plug connection RPM sensor (1) Plug connection Auxiliary rpm sensor (2) Function The rpm sensor consists of a permanent magnet and a coil with a high number of wind- ings. The magnet “touches” the rotaring component to be measured, normally a crown gear or grooved ring gear, with its magnetic field. If the EDC-M(S) 5 system is fitted, the marine engine is provided with 6 rivets on the flywheel. When a groove moves past the sensor, the magnetic flux increases and, conversely, decreases in the gaps between the grooves. This generates an induction voltage in the sensor coil which is measured by the electronic control.
The distance between the sensor and the grooved ring gear is approx. 1 mm. Two rpm sensors are required to ensure reliable operation of the EDC system. Both rpm sensors are installed in the flywheel housing. A distinction is made between the rpm sensor and the auxiliary rpm sensor. The signals of the auxiliary rpm sensor are used only for redundant engine speed sens- ing. Caution: The locations of the speed pickup (1) and the auxiliary speed pickup (2) must not be mixed up! 20