Mercury 4 FourStroke Manual page 60

NOTE: If oil level is at the add mark, add 100 ml (3 oz) of oil.
a
b
NOTE: Under certain conditions, the operating temperature of
four‑stroke outboard engines may not get hot enough to
evaporate the normal fuel and moisture that accumulate in the
crankcase. These conditions include operating at idle for long
periods, repeated short trips, slow speed or quick stop‑and‑go
operation, and operating in cooler climates. This additional fuel
and moisture that collects in the crankcase eventually ends up
in the oil sump and will add to the total volume of oil that
appears on the dipstick reading. This increase in oil volume is
known as oil dilution. Outboard engines can typically handle
large amounts of oil dilution without causing durability problems.
However, to ensure extended life of the outboard engine,
Mercury recommends that the oil be changed regularly following
the oil change interval and using the recommended oil quality. It
is further recommended that if your outboard is operated
frequently in the conditions described above, that more frequent
oil change intervals be considered.
3. Install the oil filler cap and tighten securely.
FUEL AND OIL
45609
50
a - Full mark
b - Add mark
eng