Flushing The Cooling System - Mercury 15 FourStroke Manual

Flushing the Cooling System

Flush the internal water passages of the outboard with fresh water
after each use in salt, polluted, or muddy water. This will help
prevent a buildup of deposits from clogging the internal water
passages.
Use a Mercury Precision or Quicksilver accessory (or equivalent)
flushing attachment.
IMPORTANT: The engine must be run during flushing in order to
open the thermostat and circulate water through the water
passages.
Rotating propellers can cause serious injury or death. Never
operate the boat out of the water with a propeller installed. Before
installing or removing a propeller, place the drive unit in neutral
and engage the lanyard stop switch to prevent the engine from
starting. Place a block of wood between the propeller blade and
the anti‑ventilation plate.
1. Remove propeller. Refer to Propeller Replacement. Install the
flushing attachment so the rubber cups fit tightly over the
cooling water intake.
a - Flushing device
MAINTENANCE
WARNING
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