Chapter Eight; Cooling Systems - Yanmar 1GM User Manual

Chapter Eight
Cooling System
8
This chapter covers service procedures for the thermo-
stat, engine wate r pu mp, seawa ter pumps, dri ve belts and
con necti ng hoses in both standard and closed cooling sys-
tems.
Cooling system flushing procedure s are provided in
Chapter Three. Drain and refill procedures are described
in C hapter Four.
Table I and Tab le 2 are located at the end ofthis chap-
ter.
NO TE
Exc ept where specified. F and D series en-
gines are included when a basic model num -
ber is specified. For example,
if
model 3GM
is called out in a p rocedure. the procedu re
also applies
10
3GMD and 3GMF.
COOLl:'\G SYSTEMS
Seawater (Sta ndard) Cool ing Syste m
All engines arc equipped with a seawater coo ling sys-
tem. The water in which the boat is bei ng operated is used
as a coolant to absorb engine heat. Water from outside the
boat passes through the water intake to the impeller-type
seawater pump located on the engine (Figure I , typical).
The seawater pump sends the water to the engine for cir-
c ulation through the engine block. head and manifold.
A
thermostat controls water circulation to provide
quick engine warm-up and maintain a constant operating
temperature.
Refer to typical coo ling system diagrams in Figure 2.
Figure 3 and Figure 4.