Following Complete Submersion; Engine Submerged While Running (Special Instructions); Freshwater Submersion (Special Instructions); Saltwater Submersion (Special Instructions) - Mercury 15 EFI FourStroke Service Manual

Following Complete Submersion

Engine Submerged while Running (Special Instructions)

When an engine is submerged while running, the possibility of internal engine damage is greatly increased. After the engine is
recovered, remove the spark plugs. If the engine fails to turn over freely when turning the flywheel, the possibility of internal
damage (bent connecting rod or bent crankshaft) exists. The powerhead must be disassembled for inspection.

Freshwater Submersion (Special Instructions)

1. Recover the engine as quickly as possible.
2. Place the engine at full tilt down.
3. Remove the cowling, including driveshaft housing covers.
4. Flush the exterior of the outboard with fresh water to remove mud, weeds, etc. Disassemble the powerhead if necessary to
clean the components.
IMPORTANT: Do not attempt to start the engine if sand has entered the powerhead.
5. Remove the spark plugs and get as much water as possible out of the powerhead. Most of the water inside the combustion
chambers can be eliminated by rotating the flywheel while the engine is tilted all the way down.
6. Remove and clean the fuel rail, idle air control, throttle body, air box, vapor recovery tank, and vapor separator tank/fuel
pump assembly.
7. Pour approximately one teaspoon of engine oil into each spark plug opening. Rotate the flywheel to distribute the oil.
8. Dry all wiring and electrical components using compressed air.
9. Change the engine oil.
10. Disassemble the starter motor, and dry all internal parts with compressed air. Be careful to not lose the brush springs.
11. Reinstall the spark plugs.
12. Reassemble the engine, and attempt to start the engine using a fresh fuel source.
• Run the outboard for a short time, and check for the presence of water in the oil. If water is present, the oil will appear
milky. Drain and replace the oil.
• Run the engine for at least one hour to eliminate any water in the engine.
• If the engine fails to start, determine if the cause is fuel related, electrical, or mechanical. Repair as required.
IMPORTANT: The engine should be run within two hours of recovery from the water, or serious internal damage will occur. If
the engine is unable to start within two hours of recovery, disassemble the engine and clean all parts. Apply oil as soon as
possible.

Saltwater Submersion (Special Instructions)

Due to the corrosive effect of saltwater on internal engine components, complete disassembly of the engine is necessary
before any attempt is made to start the engine.

Fuel Requirements

IMPORTANT: Use of improper gasoline can damage your engine. Engine damage resulting from the use of improper
gasoline is considered misuse of the engine and will not be covered under the limited warranty.
Fuel Ratings
Mercury outboard engines will operate satisfactorily with any major brand of unleaded gasoline that meets the following
specifications:
USA and Canada ‑ A posted pump octane rating of 87 (R+M)/2, minimum, for most models. Premium gasoline 91 (R+M)/2
octane is also acceptable for most models. Do not use leaded gasoline.
Outside USA and Canada ‑ A posted pump octane rating of 91 RON, minimum, for most models. Premium gasoline (95 RON)
is also acceptable for all models. Do not use leaded gasoline.
Using Reformulated (Oxygenated) Gasoline (USA Only)
Reformulated gasoline is required in certain areas of the USA and is acceptable for use in your Mercury Marine engine. The
only oxygenate currently in use in the USA is alcohol (ethanol, methanol, or butanol).
Gasoline Containing Alcohol
Bu16 Butanol Fuel Blends
Fuel blends of up to 16.1% butanol (Bu16) that meet the published Mercury Marine fuel rating requirements are an acceptable
substitute for unleaded gasoline. Contact your boat manufacturer for specific recommendations on your boat's fuel system
components (fuel tanks, fuel lines, and fittings).
90-8M0125265 eng NOVEMBER 2017 © 2018 Mercury Marine
General Information
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