Stern Drive Unit Seawater Pickup Pump Output Test - Mercury 305 CID Service Manual

Stern Drive Unit Seawater
Pickup Pump Output Test
If an overheating problem exists, use this test to de-
termine if a sufficient amount of water is being
supplied to cool engine.
IMPORTANT: The following information should
be observed before proceeding with test:
BOAT MUST BE IN THE WATER FOR THIS
TEST. This test CANNOT BE performed with a
flush-test device and water hose.
The ability of this test to detect a problem is
greatly dependent upon the accuracy in
which it is performed. An error in setting the
engine RPM, timing the test or measuring the
water output will affect the overall accuracy
of the test and may produce misleading re-
sults. To help ensure accurate results, a shop
tachometer with an error of less than 5%
should be used. The boat tachometer defi-
nitely should not be used as its accuracy is
questionable. A stop watch should be used to
time the duration of the test to help ensure
that the accuracy is maintained within one
second. An 8 U.S. qt. (7.6 L) or larger capacity
container should be used to measure water
output.
Due to the manner in which this test is per-
formed, it may not be possible to detect a
marginal condition or a high-speed water
pump output problem.
Index
6A-6 - SEAWATER COOLING MODELS
1. Remove water inlet hose, which runs between
gimbal housing water tube and engine, and re-
place with another hose of same diameter, but
approximately 3 ft. (1 m) longer. Hose should be
wire reinforced or of adequate wall thickness to
prevent it from kinking when performing test.
Clamp hose at gimbal housing water tube only.
Do not clamp hose at engine end.
a
a - Water Tube
b - Hose Clamp
c - Water Hose
2. Place an 8 U.S. qt. (7.6 L) or larger container near
unclamped end of hose.
! CAUTION
Do not run engine for more than 15 seconds with
hose disconnected, in next step, as internal dam-
age to engine and exhaust system may result.
3. With assistance of another person, start engine
and adjust speed to exactly 1000 RPM while
holding unclamped end of hose on connection on
engine. Remove hose from connection on engine
and direct water flow into container for exactly 15
seconds. At the end of 15 seconds, direct the wa-
ter flow overboard, return engine to idle and stop
engine. Reconnect hose to engine.
4. Measure quantity of water discharged into con-
tainer and compare with specifications given in
chart following.
c
b
72614
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