Cylinder; 20-Hour Break-In Period; After 20 Hour Break-In Period; 20-Hour Checkup - MerCruiser GM4 Service Manual

4 Cylinder

20-Hour Break-In Period

IMPORTANT: The first 20 hours of operation is the
engine break-in period. Correct break-in is essen-
tial to obtain minimum oil consumption and maxi-
mum engine performance. During this break-in
period, the following rules must be observed:
Do not operate below 1500 RPM for extended pe-
riods of time for first 10 hours. Shift into gear as
soon as possible after starting and advance
throttle above 1500 RPM if conditions permit safe
operation.
Do not operate at one speed consistently for ex-
tended periods.
Do not exceed 3/4 throttle during first 10 hours.
During next 10 hours, occasional operation at full
throttle is permissible (5 minutes at a time maxi-
mum).
Avoid full throttle acceleration from idle speed.
Do not operate at full throttle until engine reaches
normal operating temperature.
Frequently check crankcase oil level. Add oil if
needed. It is normal for oil consumption to be high
during break-in period.
After 20-hour break-in period, drain crankcase oil
and replace oil filter (see "Maintenance"). Fill
crankcase with correct oil (see "Specifications").

After 20 Hour Break-In Period

To help extend the life of your MerCruiser power
package, the following recommendations should be
considered:
Use a propeller that allows the engine to operate at
or near the top of the maximum RPM range (See
Specifications) when at full throttle with a normal
boat load.
Operation at 3/4 throttle setting or lower is recom-
mended. Refrain from prolonged operation at
maximum (full throttle) RPM.
Index
90-816462 2-695

20-Hour Checkup

After first 20 hours of operation, an Authorized Mer-
Cruiser Dealer should be contacted for the following
maintenance. The boat owner is responsible for any
charges.
Change crankcase oil and filter.
Check all fluid levels.
Cooling Systems - Inspect all hoses for damage
and deterioration; check all hose clamps for ade-
quate tightness.
Check carburetor adjustment.
Inspect ignition system and timing.
Check for loose, missing or damaged parts.
Check shift and throttle cable adjustments - Lubri-
cate and inspect for loose, damaged or missing
parts.
Steering System - Lubricate and inspect for loose,
damaged or missing parts.
Inspect all drive belts.
Check engine alignment.
Complete Engine Exhaust System - Inspect exter-
nally for damage and deterioration; check all hose
clamps for adequate tightness.
Front engine mounts-Tighten securely and ensure
that thejam nut is tight.
Rear mounts-Check torque to 35-40 lb. ft. (47-54
N·m).
Retorque gimbal ring clamping U-bolt to 55 lb. ft.
(74 N·m).
MAINTENANCE - 1B - 5