Engine Over-Speed Limiter - Mercury 40 SeaPro Operation, Maintenance & Installation Manual

ENGINE OVERHEAT
If the engine overheats, the warning horn will sound and the warning system
will automatically limit the engine speed to 2500 RPM. Immediately reduce
throttle speed to idle. Shift outboard 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 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. Have the outboard checked by your dealer. Operating the
engine while overheated 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. Operating an
overheated engine 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, consult your dealer. Operating an overheated
engine will cause engine damage.
Engine Over‑Speed Limiter
The outboard is equipped with an engine over‑speed limiter which limits the
engine maximum RPM. This will protect the engine from mechanical damage.
Some causes of engine over‑speed are as follows:
• Propeller ventilation.
• A propeller which 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 over‑speed limiter is activated, the engine timing will be
momentarily retarded to decrease the engine speed. Excessive over‑speed
(above 6000 RPM) will result in cutout of the cylinders to prevent operation
above this limit.
FEATURES AND CONTROLS
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