90-859494 Service Manual – Mercury/Mariner Optimax 115–150HP (1999)

The Mercury Optimax Service Manual (part number 90-859494) is the genuine factory guide for 1999-model 115HP, 135HP, and 150HP Optimax direct-injected outboards with serial numbers 0G960500 and above. Published by Mercury Marine, this manual delivers manufacturer-approved procedures for reliable, accurate servicing.

Inside you’ll find detailed instructions for powerhead repairs, ignition timing, oil delivery systems, fuel rails, SmartCraft sensors, cooling circuits, and lower-unit service. Easy-to-read exploded diagrams help you identify each component. Torque values and part tolerances are listed clearly so you can perform repairs confidently and correctly.

Use this Mercury Optimax Service Manual for routine operations such as injector cleaning, oil pump testing, diaphragm replacement, and crankshaft inspection. Troubleshooting charts guide you quickly from symptoms to solutions, reducing workshop time and preventing unnecessary part replacements.

Because Mercury engineers wrote this manual, all procedures follow factory design standards. Durable pages resist oil and moisture, making the book ideal for busy marine workshops or hands-on owners working from home.

Arizona Outboard Dismantlers supplies authentic manuals like this so you can protect your engine investment, maintain top performance, and stay on the water season after season.