Propeller Information; Water Testing New Engines - Mercury MerCruiser MCM 454 Mag MPI Service Manual

GENERAL INFORMATION

Propeller Information

Refer to the "Propeller" section in appropriate MerCruiser Sterndrive Service Manual, or
order publication 90-86144-92, "Everything you need to know about propellers."
Changing diameter, pitch or coupling of a propeller will affect engine rpm and boat perfor-
mance. The blade configuration also will affect performance. Two like propellers, same pitch
and diameter, from two different manufacturers will perform differently.
It is the responsibility of the boat manufacturer and/or selling dealer to equip the boat with
the correct propeller to allow the engine to operate within its specified rpm range at
wide-open-throttle (W.O.T.).
Because of the many variables of boat design and operation, only testing will determine the
best propeller for the particular application.
To test for correct propeller, operate boat (with an average load onboard) at W.O.T. and
check rpm with an accurate tachometer. Engine rpm should be near top of the specified
range so that, under heavy load, engine speed will not fall below specifications.
If engine exceeds the specified rpm, an increase in pitch and/or diameter is required.
If engine is below rated rpm, a decrease in pitch and/or diameter is required.
If a propeller is installed that does not allow engine rpm to reach the specified
full-throttle rpm range, the engine will "labor" and will not produce full power.
Operation under this condition will cause excessive fuel consumption, engine
overheating and possible piston damage (due to detonation). Conversely, installing
a propeller, allowing engine to run above the specified rpm limit, will cause
excessive wear on internal engine parts which will lead to premature engine failure.

Water Testing New Engines

Use care during the first 20 hours of operation on new MerCruiser engines or possible
engine failure may occur. If a new engine has to be water-tested at full throttle before the
break-in period is complete, follow this procedure.
1. Start engine and run at idle rpm until normal operating temperature is reached.
2. Run boat up on plane.
3. Advance engine rpm (in 200 rpm increments) until engine reaches its maximum rated
rpm.
IMPORTANT: Do not run at maximum rpm for more than 2 minutes.
Index Index
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SERVICE MANUAL NUMBER 23
90-861326--1 MARCH 1999