MAINTENANCE
SERVICE MANUAL NUMBER 25
90-861328--1 NOVEMBER 1999
Page 1B-11
CA693
Crankcase Oil
To help obtain optimum engine performance and to provide maximum protection, we
strongly recommend the use of Quicksilver 4-Cycle 25W-40 Marine Engine Oil. This oil is
a special blend of 25-weight and 40-weight oils for marine engines. If not available, a good
grade, straight weight, detergent automotive oil of correct viscosity, with an API
classification of SH,CF/CF-2, may be used.
In those areas where Quicksilver 4-Cycle 25W-40 Marine Engine Oil or a recommended
straight weight oil are not available, a multiviscosity 20W-40 (SH, CF/CF-2) or, as a second
but less preferable choice, 20W-50, with API service ratings of SH, CF/CF-2 may be used.
IMPORTANT: The use of non-detergent oils, multi-viscosity oils (other than Quicksil-
ver 25W-40 or a good quality 20W-40 or 20W-50), synthetic oils, low quality oils or oils
that contain solid additives are specifically not recommended.
The chart below is a guide to crankcase oil selection. The oil filter should always be changed
with oil.
70534
Quicksilver 4-Cycle Marine Engine Oil
SAE 20W
SAE 30W
SAE 40W
32
°
F
0
°
C
50
°
F
10
°
C
AIR TEMPERATURE
Overfilled Crankcase Oil
Overfilled crankcases (oil level being too high ) can cause a fluctuation or drop in oil pressure
and rocker arm “clatter” on Mercury MerCruiser engines. The over-full condition results in
the engine crankshaft splashing and agitating the oil, causing it to foam (become aerated).
The aerated oil causes the hydraulic valve lifters to “bleed down.” This, in turn, results in
rocker arm “clatter” and loss of engine performance, due to the valves not opening properly.
Care must be taken when checking engine oil level. Oil level must be maintained between
the ADD mark and the FULL mark on the dipstick. To ensure that you are not getting a “false
reading,” make sure the following steps are done before checking the oil level.
•
Boat “at rest” in the water, or
•
If boat is on a trailer, raise or lower bow until the boat is setting at the approximate angle
that it would be if setting “at rest” in the water.
•
Allow sufficient time for oil to drain into the crankcase if engine has just been run or oil
has just been added.
