2003 Johnson ST 6/8 HP 4 Stroke Outboards Service Manual, PN 5005471, Page 204Get this manual
GEARCASE LUBRICANT
LUBRICANT
Draining
IMPORTANT: Gearcase lubricant may be under
pressure andor hot if plug is removed from recently operated outboardTake precaution to avoid injuryRemove the lubricant level plug, then the lubricant drainfill plug, and drain the lube from the gearcase into containerInspect the lube for metal chips
Inspection
Inspect the lubricant for water contamination Water in the lubricant can cause milky appearance, however normal aeration can also cause the same appearanceTo verify water contamination, drain lubricant into suitable glass containerAllow the drained oil to settle for minimum of one hour to determine if there is abnormal amount of water in the oilSome gearcase lubricants are designed to mix with volume percentage of water from normal water vapor condensation within the gearcaseRefer to LEAK TEST PROCEDURE
Overheated lubricant will give the lubricant black color and burned odorInternal gearcase inspection is recommended when lubricant is contaminated or shows signs of failure