Mercury 200 OptiMax Jet Drive, Service Manual, Page: 110 / 391

Ignition
90-8M0050731 MAY 2011 Page 2A-29
IMPORTANT: The Guardian System cannot guarantee that powerhead damage will not occur when adverse operating conditions
are encountered. The Guardian System is designed to 1) warn the boat operator that the engine is operating under adverse
conditions and 2) reduce power by limiting maximum RPM in an attempt to avoid or reduce the possibility of engine damage. The
boat operator is ultimately responsible for proper engine operation.
Guardian System Activation
Condition Result
Engine overheat
Engine power level can be reduced to any percentage down to a fast idle, if overheat condition
persists.
Air compressor overheat Warning horn is activated, but there is no power reduction.
Block water pressure low
Engine power level can be reduced to any percentage down to a fast idle, if overheat condition
persists.
Throttle position sensor failure
If the throttle position sensor fails or becomes disconnected, power will be limited to a
maximum of approximately 4500 RPM. When the TPS is in the fail mode, the PCM will use
the MAP sensor for a reference to determine fuel calibration.
Temperature sensor (cylinder
head and air compressor) failure
If a temperature sensor should fail or become disconnected, power will be limited to a
maximum of approximately 4500 RPM.
Battery voltage (too high or too
low)
Battery voltage greater than 16 volts or less than 10 volts will result in engine output power
being reduced. The higher or lower the voltage is outside of these parameters, the greater
the percentage of power reduction. In an extreme case, power could be reduced to a fast
idle.
Oil pump failure
If the oil pump fails or an open circuit occurs between the pump and the PCM, engine power
will be reduced to a fast idle.
Engine Overspeed Protection System
The system is activated when the engine speed exceeds the maximum allowable RPM.
Overspeed activation for the outboard will result in the warning horn sounding continuously and the engine speed automatically
being reduced to within allowable limits.
Warning Horn Signals
When the key switch is turned to the "ON" position, the horn will be audible for a moment as a test to show the horn is working.
The warning horn will emit either a continuous beep or intermittent short beeps. This will alert the operator and help identify the
following listed situations. For visual display of the specific engine functions and additional engine data, refer to the helm‑mounted
SmartCraft product for more information.