2003 Johnson ST 6/8 HP 4 Stroke Outboards Service Manual, PN 5005471, Page 58Get this manual
MAINTENANCE SUBMERGED ENGINES Every 30 minutes operate outboard at full throttle for one minuteDO NOT exceed recommended maximum engine RPMto returning the outboard to serviceElectric starters should be disassembled, cleaned, flushed with clean water, and treated with water displacing electrical spray prior to reassemblyRemove carburetor for draining, disassembly and cleaningDisconnect fuel supply hose from outboard Drain and clean all fuel hoses and fuel tanksRefill fuel tank with fresh fuelClean or replace fuel filter element as neededInject small amount of outboard lubricant into spark plug holes and install new spark plugsReinstall all removed or disconnected partsRun the outboard below 1500 RPM for one-half hour on 25:1 fueloil mixture
IMPORTANT: Torque the cylinder head screws after the outboard break-in periodTorque after outboard has been run and the cylinder heads have cooled to the touch
SUBMERGED ENGINES
Once an outboard has been submerged in fresh or salt water, it must be serviced within three (3) hours of recoveryImmediate service can minimize the corrosive affect that air has on the polished surfaces of the crankshaft, connecting rods, and internal powerhead bearings