Propeller Replacement; Spark Plug Inspection; Carburetor Adjustments - Mercury 4 Manual

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MAINTENANCE
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PROPELLER REPLACEMENT

WARNING
If the propeller shaft is rotated while the engine is in gear, there is the pos-
sibility that the engine will crank over and start. To prevent this type of
accidental engine starting and possible serious injury caused from being
struck by a rotating propeller, always shift outboard to neutral position
and remove spark plug leads when you are servicing the propeller.
1
Remove the spark plug lead to prevent engine from starting.
2
Move gear shift lever into neutral.
3
Straighten and remove cotter pin (a).
4
Place a block of wood between gear case and propeller to hold propeller and
remove propeller nut (b).
5
Pull propeller (c) straight off shaft. If propeller is seized to the shaft and cannot
be removed, have the propeller removed by an authorized dealer.
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d
c
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PROPELLER REPLACEMENT (CONTINUED)
6
Coat the propeller shaft with Quicksilver or Mercury Precision Lubricants
Anti-Corrosion Grease or 2-4-C Marine Lubricant with Teflon.
IMPORTANT: To prevent the propeller hub from corroding and seizing to the
propeller shaft, especially in salt water, always apply a coat of the recommended
lubricant to the entire propeller shaft at the recommended maintenance intervals
and also each time the propeller is removed.
7
Install front thrust washer (a), propeller (b), rear thrust hub (c) and propeller nut
(d) onto the shaft.
8
Place a block of wood between gear case and propeller to prevent rotation and
tighten propeller nut. Secure propeller nut to the shaft with cotter pin (e).
90-10102R30
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SPARK PLUG INSPECTION AND REPLACEMENT
Avoid serious injury or death from fire or explosion caused by a dam-
aged spark plug boot (a). A damaged spark plug boot can emit sparks.
Sparks can ignite fuel vapors under the engine cowl. To avoid damag-
ing the spark plug boot, do not use any sharp object or metal tool
such as pliers, screwdriver, etc. to remove the spark plug boot.
1
Remove the spark plug boot (a) by twisting the rubber boot slightly and pull off.
2
Remove the spark plug to inspect and clean. Replace spark plug if electrode
is worn or the insulator is rough, cracked, broken, blistered or fouled.
3
Set the spark plug gap. See Specification Chart in General Information Section.
4
Before reinstalling spark plug, clean away dirt on the spark plug seat. Install
plug finger tight, and tighten 1/4 turn or torque to 20 lb. ft. (27 N·m).
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CARBURETOR ADJUSTMENTS

Slow Speed Mixture Adjustment
1
Before starting engine, turn the slow speed mixture screw (a) in until it is lightly
seated then back it out 1-1/2 turns.
2
With the boat tied securely to dock, start engine and allow it to warm up.
3
Shift the outboard to forward gear and reduce engine speed to idle.
4
Turn the slow speed mixture screw slowly in until the engine starts to misfire
or stall due to a lean mixture. Note the position of the screw slot.
5
Turn the slow speed mixture screw slowly out until the engine starts to "load
up" or fire unevenly due to a rich mixture.
6
Set the slow speed mixture screw midway between the rich and lean setting.
When in doubt, set the mixture slightly rich rather than too lean.
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WARNING
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