Mercury 350 MAG MPI Horizon, Service Manual

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Because of possible adverse effects of alcohol in gasoline, it is recommended that only alcohol-free gasoline
be used where possible. If only fuel containing alcohol is available, or if the presence of alcohol is unknown,
increased inspection frequency for leaks and abnormalities is required.
IMPORTANT: When operating a Mercury MerCruiser engine on gasoline containing alcohol, storage of
gasoline in the fuel tank for long periods should be avoided. Long periods of storage, common to boats,
create unique problems. In cars alcohol-blend fuels normally are consumed before they can absorb
enough moisture to cause trouble, but boats often sit idle long enough for phase separation to take
place. In addition, internal corrosion may take place during storage if alcohol has washed protective oil
films from internal components.
CC540
Seacock Size Recommendation
Seacock used must have an internal cross-sectional area equal to or greater than hose to prevent restricting
waterflow. Install valve in an area where it will be easily accessible and supported adequately to prevent hose
fatigue. A 1-1/4 in. (32 mm) brass ball or gate valve is suggested.
CC16
Sea Strainer Recommendation
Strainer used must be of sufficient size to ensure that an adequate supply of water will be maintained for cooling
engine. A minimum of 30 gallons per minute (114 liters per minute) flow rate, is required.
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 multi-viscosity 20W-40 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 Quicksilver 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 when changing
engine oil.
75796
Quicksilver 4-Cycle 25W-40 Marine Engine Oil
SAE 20W
SAE 30W
SAE 40W
32
°
F
0
°
C
50
°
F
10
°
C
AIR TEMPERATURE