1999 "EE" 90, 115 FFI, 150, 175 V4, V6 FFI Outboards Service Manual, P/N 787024, Page 57Get this manual
Electronic Control Unit (ECU)
The Electronic Control Unit (ECU) is located at the top rear of the powerheadIt has two 24-pin engine harness connectors It's water-cooled microprocessor that receives sensor, switch, and electrical signals that provide information on engine operating conditionsAll provide data to help the ECU control engine operating parameters such as spark advance, fuel flow, and oilingThe ECU also sends electrical commands to various powerhead components to control engine operationWhen failure is detected, service code is storedThese inputs include: Throttle Position Shift Interrupt (V6 only) Air Temperature Crankshaft Position Water Temperature Oil Pressure ECU Temperature Battery 12 Volts Alternator 26 Volts Read Only Memory (ROM) Verification Barometric Pressure
The ECUbesides controlling engine operation, has number of other important programmed functionsIt: Stores service codes Activates the S.L.OWTM Warning System Provides choke-less cold starting Outputs real-time diagnostic data Controls the System Check TM Engine Monitor gauge lights Generates tachometer signal Prevents excessive engine RPM Features 5-hour, break-in oil ratio that's twice the normal rate Controls electric fuel pump operation Records engine operating hours