2004 SR Johnson 2-stroke 40, 50HP Service Manual, Page 64Get this manual
MAINTENANCE COOLING SYSTEM
COOLING SYSTEM
Monitor the condition of cooling system components regularlyThe outboard cooling system consists of: water intake screens; overboard water flow indicator; water pump; internal water passages; thermostat; and external water hoses and fittings
Shift the outboard to NEUTRAL with the propeller removedTurn water supply onSTART outboardRun it at IDLE onlyFlush the outboard for at least five minutes and check the water pump indicator and make sure there is steady stream of water flowing
Flushing
Flush the outboard with fresh water following each use in brackish, salt, or polluted water to minimize the accumulation of scale and silt deposits in cooling system passagesThe outboard can be flushed on the trailer or at dockside1
Water pump indicator
IMPORTANT: The outboard must be located in well ventilated area with appropriate ground drainage during the flushing proceduresKeep water inlet pressure between 20 to 40 psi (140 to 275 kPa)