Seawater Section - Mercury MerCruiser MCM 454 Mag MPI Service Manual

SERVICE MANUAL NUMBER 23

Seawater Section

Cooling efficiency of an engine with closed cooling is greatly dependent upon heat transfer
through the tubes within the heat exchanger. During engine operation, contaminants within
the seawater (such as salt, silt, lime, etc.) collect on the inside of the tubes, thus reducing
heat transfer and greatly decreasing heat exchanger efficiency. It is, therefore, recom-
mended that the seawater section of the heat exchanger be cleaned at least once every two
years or whenever decreased cooling efficiency is suspected, as follows:
1. Remove bolts which secure end plates to each end of heat exchanger, then remove end
2. Clean water passages in heat exchanger by inserting a suitable size wire brush into
3. Apply Quicksilver Perfect Seal to both sides of new end plate gaskets, then reinstall end
Avoid seawater pickup pump impeller damage. DO NOT operate engine without
water being supplied to seawater pickup pump.
4. With boat in the water and/or cooling water properly supplied to seawater pickup pump,
Index
90-861326--1 MARCH 1999
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plates, seal washers and gaskets. Discard seal washers and gaskets. Clean gasket
material from end plates and heat exchanger.
b
c
a - Heat Exchanger
b - Sealing Washer
c - End Cap
d - Gasket
each passage. Use compressed air to blow loose particles out of water passages.
plates, using new gaskets and seal washers. (Be sure to install seal washers between
end plates and gaskets.) Torque end plate bolts to specifications.
start engine and inspect for leaks.
CLOSED COOLED (FRESH WATER) MODELS
a
d
CAUTION
71515
Page 6B-15