Mercury Mariner 4, 5, and 6HP 4-Stroke Factory Service Manual, Page 16Get this manual
MAINTENANCE
Flushing The Cooling System
Flush the internal water passages of the outboard with fresh water after each use in salt, polluted, or muddy waterThis will help prevent buildup of deposits from clogging the internal water passages
NOTE: Do not run the engine while flushing the cooling system1Remove plug and gasket and thread-in hose coupling2Attach water hose to the hose couplingTurn on the water gently and flush the cooling system for to minutes3Remove the thread-in hose coupling and reinstall plug and gasket
aPlug and GasketHose Coupling
Fuel System