1998 Johnson Evinrude "EC" 150, 175 FFI Service Manual, P/N 520211, Page 43Get this manual
The Power Distribution Panel supplies the 12 and 26 volts necessary to operate the ECU and ignition moduleIt also contains number of relays and fuses to protect or control these circuitsThe ignition module mounts three coil assemblies, and contains the circuits necessary to supply them with voltage and to fire themThe module receives switched battery 12V and rectifier regulator 26V, both from the Power Distribution PanelSix module wires connect to the ECU to allow the ECU to control individual cylinder firingThe coils ground through the module mounting bracket, but the module also requires an external ground wire FFI Combustion Process
The FFI combustion process functions in two modes; stratified and homogeneousDuring stratified operation (below approximately 15 throttle), multiple plug firings occur for each cylinder combustion eventSpark is timed to occur as fuel reaches the spark plug tip, then is programmed to continue in multi-strike modeDue to fuelair density at low RPM, and fuel actually spraying on the plug tip, repeated plug firing ensures complete mixture combustionDuring homogeneous operation (above approximately 15 throttle), the fuel injectors supply fuel earlier in the firing sequencePistons are farther down the cylinder, and gases are mixed by turbulenceIn this mode the mixture is more combustible, so fewer firings per cylinder combustion event will occurVery low amperage is required to sustain either stratified or homogeneous operation