Seawater Inlet Recommendations; Transom Mounted Or Through-Hull Seawater Pickups And Hose; Seacock (Seawater Inlet Valve); Sea Strainer - Mercury MerCruiser MCM 454 Mag MPI Service Manual

SEAWATER COOLED MODELS

Seawater Inlet Recommendations

Transom Mounted or Through-Hull Seawater Pickups and Hose

Water pickup must be large enough to permit sufficient water flow to engine seawater pickup
pump for adequate engine cooling [30 gal. per min. (114 L per min.) minimum]. Pickup also
must supply a positive head while underway.
Do not install water pickup directly in line with propeller, as pickup may create
turbulence and allow air to flow into the "propeller slipstream." This will cause
propeller ventilation and will adversely affect boat performance.
Water pickup should be located as close to seawater pickup pump inlet as possible and in
an area where an uninterrupted, solid stream of water will flow past when boat is underway.
Connect water pickup to seawater pickup pump inlet with 1-1/4 in. (32 mm) I.D. wire rein-
forced hose of adequate wall thickness to prevent it from collapsing from pump suction. Be
sure to secure hose connections with hose clamps.

Seacock (Seawater Inlet Valve)

If a seacock is being used, it must be installed between water pickup and seawater pickup
pump (or sea strainer), to allow operator to shut off the seawater in case of a leak or when
boat is not in use. This will allow the operator to flush or drain the engine, or clean the sea
strainer while boat is in the water. Seacock used must have an internal cross-sectional area
equal to or greater than hose to prevent restricting water flow. Install seacock in an area
where it will be easily accessible and self-supporting to prevent hose fatigue.
Seacock (with Thru-Hull Pickup Shown)

Sea Strainer

If boat is equipped with a sea strainer, it must be of sufficient size to ensure that an adequate
supply of water is maintained for engine cooling. Install seawater strainer in an area where
it will be easily accessible for inspection and cleaning. Strainer should be installed in water
inlet hose after water inlet valve to allow operator to shut off water when cleaning strainer.
Index
Page 6A-4
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a - Hose Connector 1-1/4 In. (32 mm) I.D. To Seawater Pump Inlet
b - Seacock 1-1/4 In. (32 mm) Brass Ball Or Gate Valve
c - Seawater Pickup
d - Direction Of Seawater Flow
CAUTION
a
b
c
SERVICE MANUAL NUMBER 23
70355
d
90-861326--1 MARCH 1999