Yanmar 1GM User Manual page 176

170
Sea water pump drive belt replacement
(except I GJI and I G.UI Oengines)
Replace the seawater drive belt as follows:
I
. Loosen
the alternator bracket and pivo t bo lts (Figure
17, typica l).
2. Move the alternator toward the eng ine and slip the belt
off the cra nkshaft and alternato r pulleys, and if equipped
with freshwater coo ling, the circulating water pump pul-
Icy.
3. Loosen the seawater pump bracket and pivot bolts
(Fi J::ure 18, typical) ,
4. Move the seawa ter pump toward the engine and slip
the belt off the crank shaft and pump pulleys.
5. Install a new belt over the pulleys.
6. Move the sea water pump away from the engine and
adju st the belt tension as described in Chapter Three.
7. Install the alternator driv e bell onto the crankshaft and
alternator pulleys. and if equi pped with freshwater coo l-
ing. the ci rculating water pump pulley.
8. Move the alternator away from the eng ine and adjust
the belt tension as described in Chapter Th ree.
SEAWATE R P UMP
All engines covered in this manual use a seawater pump
( Ftgu re 19. typical). The seawater pump on IGM and
IGMIO eng ines is driven by the end of the oil pum p
drives haft. All other eng ines use a belt-driven seawater
pump . A rubber impeller inside the pump mov es wate r
through the pump. The pump draws water into the intake
port as the impe ller vanes flex outward. and it pumps wa-
C IIAPTE R EIG IIT
-{. '
.
-.
'~.
, ito
··'l.J..
Bolts
L-+---~D
tcr out o f the discharge port as the impe ller vanes flex
inward .
as shown in Figure 20.
The impeller on ly operates in a counterclockwise rota -
tion (viewed from cover side of pump) and remains in a
flexed (compressed) position at all times. Over time, this
causes the impeller to take a set in one direction . Turning
an impel ler over and attempting to tum it aga inst its natu -
ral set will cause premature impeller failure and engine
damage from over heat ing.
Rep lace the impeller every time the water pump is d is-
assemb led. The impeller must onl y be reused if there is no
other option. If the impeller must be reused . reinstall the
impeller in its o rigina l pos ition.
Overh eating and exte nsive engi ne dama ge can result
from a faulty water pump. Th erefore, it is high ly recom-
mended that the water pump impeller, seals and gaskets be
inspected after every 1,500 hours
of operation as a pre-
ventive maintenance meas ure. Individual operating con-
ditions ma y dictate that the pump will requ ire serv ice
mo re often.