Mercury 15 EFI FourStroke, Service Manual

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If a caution state is detected, the warning system will sound the horn for six one‑second intervals, and then remain silent. The
warning light will flash six times, in sync with the horn, and then will repeat every five minutes.
Caution state sequence
a - Horn and light (on or off); light repeats every five
minutes
b - Time (in seconds)
If a critical state is detected, the warning system sounds the horn for six seconds and then turns off. The warning light will turn
on and remain lit as long as the fault is active.
Critical state horn sequence
a - Horn (on or off); light remains lit
b - Time (in seconds)
Engine Overheat
If the engine overheats, immediately reduce throttle speed to idle. Shift the outboard into neutral and check for a steady stream
of water coming out of the water pump indicator hole.
62870
If no water is coming out of the water pump indicator hole, or flow is intermittent, stop the engine and check the cooling water
intake holes for obstruction. If no obstruction is found, there may be a blockage in the cooling system or a water pump problem.
Operating the engine while overheated will cause engine damage.
If a steady flow of water is coming out of the water pump indicator hole and the engine continues to overheat, service is
required. Operating an overheated engine will cause engine damage.
NOTE: Should overheating occur and you are stranded, stop the engine and allow it to cool down. This will usually allow some
additional low speed (idle) running time before the engine starts to overheat again.
Low Oil Pressure
The warning system will be activated if the oil pressure drops too low. First, stop the engine and check the oil level. Add oil if
necessary. If the oil level is within the operating range and the warning horn continues to sound, service is required. Engine
speed will be limited to 2800 RPM, however, you should not continue to run the engine.
Engine Overspeed Limiter
Some causes of engine overspeed are as follows:
•
Propeller ventilation
• A propeller that has an incorrect pitch or diameter
• Propeller hub slippage
• Outboard mounted too high on the transom
• Tilting the outboard out beyond a vertical position
• Cavitation of the propeller due to rough water or obstruction in the boat hull
When the engine overspeed limiter is activated, the engine timing will be momentarily retarded to decrease the engine speed.
Excessive overspeed will result in the momentary removal of ignition to prevent operation above the RPM limit.
ON ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
1
1
1
1
1
1
1
1
1
1
1
OFF
33402
a
b
53403
a
b
ON
6
OFF
General Troubleshooting
Page 1E-6 © 2018 Mercury Marine 90-8M0125265 eng NOVEMBER 2017