1999 "EE" Evinrude 70HP 4-Stroke Service Manual, P/N 787023, Page 49Get this manual
Oil Pressure Switch
[] The switch CD monitors oil pressure, and will signal the ECU if pressure drops below its threshold limit of 14.5 PSI (100 20 kPa)It's on the cylinder block directly behind the ECUThe switch is normally closed, oil pressure opens itWhen the ECU receives loss of oil pressure signal, System CheckTM turns on theNO OIL" LED, and the engine will go into S.L.OWabove 3000 RPM
Ignition System Operation
The engine's Ignition Control System consists of the ECU and sensors such as the Cylinder Temperature sensor, MAP (Manifold Absolute Pressure) sensor, CKP (Crankshaft Position) sensor and CTP (Closed Throttle Position) switch This is "waste spark" system; i.etwo cylinders fire simultaneously, one on compression stroke, another on an exhaust strokeThe ECU monitors various engine conditions, controls ignition timing, and contains ROM (Read Only Memory)ROM stores the map (data) for the basic ignition timing at various manifold absolute pressures and engine speedsBasic ignition timing, after being read out from ROM from CKP and MAP signals, is further modified by signals from compensating sensor (cylinder temperature) to obtain the final ignition timingThis is called "forecast control" and is based on periodic cycle of engine speed sensed by the CKP (Crankshaft Position) sensorBasic Ignition Timing