Service manual

TROUBLESHOOTING
SERVICE MANUAL NUMBER 26
90-861329--1 MARCH 1999 Page 1C-35
Insufficient Water Flow From Alpha One Sterndrive Unit
Seawater Pickup Pump
Cause Special Information
Seawater shutoff valve partially or fully
closed (if equipped)
Water pickup clogged with foreign material
Kinked or broken bell housing to gimbal
housing water tube hose
Corroded through gimbal housing water
tube
Water pickup inserts warped. (Engine will
overheat while boat is underway.)
Water pickup must not protrude above
gear housing surface or inserts will create
an irregular or turbulent water flow over
the water pickup holes. Consequently, this
may cause loss of cooling water and
subsequent engine overheating. This
condition can be identified by cavitation
burn (pitting or erosion) on the gear
housing in the area aft of the water pick
up.
Damaged gear housing or accessories
improperly installed on boat bottom or
transom (speedometer pick up, depth
sounder transducer, etc.) Substantial
amount of barnacles or other marine
growth on gear housing or boat bottom.
(Engine will overheat while underway only)
An object or an irregularity on boat or gear
housing in area close to to water pickups
could create turbulence in water flow
going to water pickups. This could aerate
the water flow and cause engine to
overheat
Sterndrive installed too high on transom or
drive unit trimmed out too far out allowing
air to be drawn into pump. (Engine will
overheat while underway only)
Contact boat company if sterndrive is too
high. Instruct operator on proper trimming
technique if unit is trimmed out too far.
Bell housing-to-driveshaft housing O-ring
missing or damaged
Faulty seawater pickup pump
Seawater pickup tube corroded through
Driveshaft housing water pocket cover
cracked
Broken impeller blade or other obstruction
in water passages (usually lodges in drive-
shaft housing water pocket cover or cross
drilled water passage).
To check cross drilled water passages in
driveshaft housing, remove plug and pipe
plug located under decal on starboard side
of housing. Drive unit must be shifted into
reverse to remove pipe plug.
Water passage in driveshaft housing
improperly drilled
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