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How To Service a Two-Stroke Outboard Motor | Engine Whisperer | Practical Boat Owner
July 12, 2025 · 27 min · 2K views
What this video covers
A 1989 Mercury 2.2 two-stroke outboard, stored for three years, is serviced from scratch by Stu Davis, PBO's engine expert.0:59 The full procedure covers spark plug removal and cleaning (wire brushes prohibited — they leave metal traces on the ceramic), carburetor removal and cleaning with brake and clutch cleaner, float valve reassembly, ignition spark testing, raw water impeller inspection, shear pin and split pin checks, and gearbox oil drain and refill with API GL5 80/90 gear oil. Davis flags milky gearbox oil as the sign of a failed water seal and confirms the oil is good when it weeps from the upper fill hole.23:51 E10 petrol is identified as the primary cause of carburetor failure in small outboards: alcohol absorbs atmospheric moisture, the petrol evaporates, and the residual water reacts with leftover oil to form gum that blocks jets.14:21 Shell V-Power is recommended for lower alcohol content.14:45 The engine uses pre-electronic points ignition, requiring a three-legged flywheel puller to access them.8:28 Fuel mix is 50:1 two-stroke oil to petrol.25:51 A brake-and-clutch-cleaner squirt into the air intake confirms whether a no-start fault is fuel- or ignition-related.17:48 The complete service takes roughly one hour.25:21
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