CIMCO OXE Diesel 125 HP, Installation Manual

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OXE 125/150/175/200 HP INSTALLATION MANUAL
PROPELLER AND GEAR RATIO SELECTION
ENGINE UNDER OR OVERLOADING
NOTE! This may affect your warranty.
Overloading of the engine through the installation of a propeller with too much
pitch is the most common source of fuel inefficiency and engine damage.
Overloading can also result from the use of a propeller with too large a diameter,
but this is less common. Overloading can result in severe engine damage. It is
important to remember that, with a diesel engine, it is the load and not the RPM
that determines fuel consumption. Therefore, continuous overloaded operation
results in an unnecessarily high fuel consumption, increased maintenance costs
and
void warranty .
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If the propeller blades have too much pitch, the engine will operate below the
normal range at full throttle.
-
If the propeller blades have too little pitch, the engine will operate above its
normal rpm range and damage from over-speeding can occur.
THEORETICAL SPEED CALCULATIONS
(((RPM / Gear Ratio) x Propeller pitch) / 1396) - slip % = theoretical speed in Knots.
Example
(((4200/1.73) * 21) / 1396) – 10 % = 32.9 knots
In this example the engine is operating at 4,200rpm. The gear ratio is 1.73:1
reducing the propeller shaft speed to 2,428rpm.
With a pitch of 21”, the theoretical speed is 36.5knots. Minus 10% slip = 32.9knots