Excessive Oil Consumption - MerCruiser 305 CID (5.0L) Service Manual

TROUBLESHOOTING

Excessive Oil Consumption

Normal consumption
Oil leaks
Oil too thin
Oil level too high
Drain holes in cylinder head plugged
Defective valve seals
Intake manifold gasket leaking
Worn valve stems or valve guides
Defective oil cooler
Defective piston rings
Defective cylinders
Excessive bearing clearance
NOTE: ENGINE CRANKCASE OIL MUST BE CHECKED AT INTERVALS SPECIFIED IN
"MAINTENANCE SCHEDULE" in SECTION 1B. It is normal for an engine to use a certain
amount of oil in the process of lubricating and cooling the engine. The amount of oil con-
sumption is greatly dependent upon engine speed, with consumption being highest at
wide-open-throttle and decreasing substantially as engine speed is reduced.
Index
Page 1C-24
Cause
SERVICE MANUAL NUMBER 24
Special Information
One quart of oil consumed in 5-15 hours
of operation at WOT (especially in a new
or rebuilt engine) is normal
Clean bilge, run engine with clean white
paper on bilge floor, locate oil leak(s)
Oil diluted or wrong viscosity
Oil will flood valve guides
Crack in cooler tubes
Glazed, scuffed, worn, stuck, improperly
installed; ring grooves worn; improper
break-in; wrong end gap
Out of round, scored, tapered, glazed;
excessive piston to cylinder clearance;
cracked piston
90-861327--1 OCTOBER 1999