Carburetor Adjustments - Mercury 20 Manual

2. Remove the spark plugs to inspect. Replace spark plug if electrode is worn or the insulator is rough,
cracked, broken, blistered or fouled.
3. Set the spark plug gap to specification.
Spark Plug
Spark plug gap
4. Before installing spark plugs, clean off any dirt on the spark plug seats. Install plugs finger tight, and then
tighten 1/4 turn or torque to specifications.
Description
Spark plug

Carburetor Adjustments

SLOW SPEED MIXTURE ADJUSTMENT
1. Remove access plug from cover.
2. Before starting engine, turn the slow speed mixture screw in until it is lightly seated then back it out 1‑1/2
turns.
3. With boat tied securely to dock, start engine and allow it to warm up.
4. Shift the outboard to forward gear while maintaining idle speed.
5. 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.
MAINTENANCE
ob00375
ob00423
1.0 mm (0.040 in.)
Nm
27
50
ob00424
lb. in. lb. ft.
20