Mercury Mariner 200, 225 Optimax Outboards Service Manual, 90-855348, Page 348Get this manual
9Pull gear housing from drive shaft housing 3Inspect gear lubricant for metal particlesPresence of small amount of fine metal particles (resembling powder) indicates normal wearPresence of larger particles (or large quantity of fine particles) indicates need for gear housing disassembly, and component inspection4Note the color of gear lubricantWhite or cream color indicates presence of water in lubricantCheck drain pan for water separation from lubricantPresence of water in gear lubricant indicates the need for disassembly, and inspection of oil seals, seal surfaces, O-rings and gear housing componentsNOTE: Gear lubricant drained from recently run gear case will be light chocolate brown in color due to agitationaerationOil which is stabilized will be clear yellow brown in color