Mercury Mariner 200, 225 Optimax Outboards Service Manual, 90-855348, Page 56Get this manual
Charging System Alternator Battery charging system is contained within the belt driven alternator, including the regulatorAt cranking speeds, electrical power for the engine is provided by the boat batteryminimum recommended size is 750, or 1,000 MCA, cold cranking amperesAbove 650 RPM for 1997 Models (550 RPM on 1998 Models), all electrical power is provided by the alternatorShould engine rpm drop below 650 (550 RPM on 1998 Models), the alternator is not capable of providing sufficient output and the battery becomes the primary source of electrical powerOnce the engine is running and rpm is 650 or higher, the engine will continue to run should the battery become shorted or disconnectedAlternator output (when hot) to the battery 2000 RPM is approximately 3338 amperes
Temperature Sensor
Three (3) temperature sensors are used to provide cylinder head temperature information to the ECMA sensor is mounted in each cylinder head and one in the air compressor cylinder headThe ECM uses this information to increase injector pulse width for cold starts and to retard timing in the event of an over-heat conditionAn ohms test of the temperature sensor would be as follows: Insert digital or analog ohmmeter test leads into both TANBLACK sensor leadsWith engine at temperature (F indicated, ohm readings should be as indi) cated 10