1999 "EE" Evinrude 70HP 4-Stroke Service Manual, P/N 787023, Page 36Get this manual
Flushing &
Do not run your engine indoorsYour engine emits toxic fumes when runningEnsure adequate ventilation by running it outdoorsFlush your engine with fresh water as soon as possible after each use in salty, polluted, or brackish water to minimize the formation of deposits that can clog cooling passagesFlush the engine on the trailer or at dockside while it is: tilted or vertical, running or stopped Outboard VerticalRunning
Prevent injury from contact with rotating propeller; remove the propeller before flushing1Place the engine in vertical position in well-ventilated area with good drainage
2Remove the plug from the flushing port3Install and garden hose
4Start the waterkeep pressure between 20-40 PSI (140-300 kPa) 5Start the engine and flush it for at least five minutesKeep its speed at or below 1500 RPM