Mercury 150 EFI Service Manual page 211

WIRING DIAGRAMS
NOTE: If you are in a stranded situation, stopping the engine and allowing it to cool back
down will usually allow some additional low speed (idle) running time before the engine
starts to overheat again.
The overheat problem must be corrected before you can resume normal operation.
PRESSURE
a -
This alarm message is displayed and the warning horn begins sounding continuously to
inform the driver that there is insufficient water pressure in the cooling system. The Engine
Guardian System will start limiting engine power.
Some causes of insufficient cooling water pressure are (1) obstructed cooling water in-
take holes (2) blockage in the cooling system or a water pump problem (3) running the
outboard with the cooling water intake holes out of the water.
NOTE: The throttle will have to be returned to idle to reset the system.
If the warning system is activated, immediately reduce throttle speed to idle. Shift out-
board into neutral and check for a steady stream of water coming out of the water pump
indicator hole.
If no water is coming out of the water pump indicator hole or flow is intermittent, stop en-
gine and check cooling water intake holes for obstruction. If no obstruction is found, this
may indicate a blockage in the cooling system or a water pump problem. Stop engine.
Operating the engine without adequate cooling water pressure will overheat the engine.
If the warning signals stop and a steady stream of water is coming out of the water pump
indicator hole, return engine to normal operation.
OVERSPEED (a)
This message is displayed and the warning horn begins sounding continuously to inform the
driver that the engine speed has exceeded the maximum allowable RPM. The system will
automatically reduce the engine speed to within the allowable limit.
NOTE: Your engine speed should never reach the maximum limit to activate the system unless
the propeller is ventilating, an incorrect propeller is being used, or the propeller is faulty.
WATER IN FUEL (b)
This message will appear and the warning horn will begin sounding a series of four beeps
every two minutes when water in the water separating fuel filter reaches the full level. The
water can be removed from the filter.
FAULT-HORN (c)
This message informs you that warning horn is not functioning correctly.
Page 2D-58
Water Pump Indicator Hole
a
b
c
a
90-883728 JULY 2001