Mercury 200 OptiMax Jet Drive, Service Manual, Page: 38 / 391

General Information
90-8M0050731 MAY 2011 Page 1C-13
Ventilation
Ventilation occurs when air is drawn from the water’s surface (excessive trim out angle) or from the engine exhaust flow (in reverse)
into the impeller blades. These air bubbles strike the impeller blade surface and cause erosion of the blade surface. If allowed to
continue, eventual blade failure (breakage) will occur.
Detonation
Detonation in a 2‑cycle engine resembles the pinging heard in an automobile engine. It can be otherwise described as a tin‑like
rattling or plinking sound.
Detonation is the explosion of the unburned fuel/air charge after the spark plug has fired. Detonation creates severe shock waves
in the engine. These shock waves often find or create a weakness: the dome of a piston, cylinder head or gasket, piston rings or
piston ring lands, piston pin and roller bearings.
A few of the most common causes of detonation in marine applications are as follows:
•
Over‑advanced ignition timing
• Use of low octane gasoline
• Lean fuel mixture at or near wide‑open throttle
• Spark plugs: heat range too hot, incorrect reach, cross‑firing
• Deteriorated or inadequate engine cooling system
• Combustion chamber deposits: result in higher compression ratio
Detonation usually can be prevented if:
•
The engine is correctly set up
• Regular maintenance is scheduled
Following Complete Submersion
Saltwater Submersion
Due to the corrosive effect of saltwater on internal engine components, complete disassembly is necessary before any attempt is
made to start the engine.
Submerged While Running
When an engine is submerged while running, the possibility of internal engine damage is greatly increased. If, after engine is
recovered and with spark plugs removed, the engine fails to turn over freely when turning the flywheel, the possibility of internal
damage (bent connecting rod and/or bent crankshaft) exists. If this is the case, the powerhead must be disassembled.
Submerged Engine (Freshwater)
IMPORTANT: Engine should be run within two hours after recovery, or serious internal damage may occur. If unable to start engine
in this period, disassemble the engine and clean all parts. Apply oil as soon as possible.
NOTE: If sand has entered the air intake on the engine, do not attempt to start the engine. Sand will cause internal engine damage.
Disassembly is required to clean all internal engine components of sand.
1. Recover the engine from the water as quickly as possible.
2. Clean the exterior of powerhead with fresh water.
3. Dry all wiring and electrical components using compressed air.
4. Drain the water from the fuel system as follows:
a. Disconnect the remote fuel hose from the engine.
b. Remove the drain plug from the vapor separator and drain the fuel/water. Install the plug after draining.
c. Remove the fuel hose from the bottom of the port side fuel rail and drain the fuel/water. Install the hose.
d. Remove the water separating fuel filter and empty the contents.
5. Drain the water from the air compressor system as follows:
a. Dry or replace the air filter for the compressor.
b. Remove the air outlet hose for the air compressor and drain the water from the compressor and hose. Install the hose.
c. Remove the air pressure hose from the bottom of the port side fuel rail and drain the water. Install the hose.
6. Drain the water from the engine as follows:
a. Remove the throttle plate assembly (four bolts). Tilt up the outboard and sponge the water out of the air plenum.
b. Remove the spark plugs from the engine.
c. Rotate the flywheel manually to blow out any water from the cylinders.