Iveco Marine Diesel Engines, Installation Handbook

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Engine with reversible blades
In this system the propeller blades hinge on the hub; the blade rotation on their axis is obtained by
means of the suitable mechanism in the hub actuated through the propeller hollow supporting shaft
(figure 13).The blade rotation is such to reverse the movement forward/backward and to keep at the
same time the same engine rotation direction.
In this case, the mechanical inverter is no longer necessary, while a reducer may be required. A decou-
pling clutch is advisable, even if the engine neutral position can be obtained by putting the propeller
blades in neutral position (idle pitch) and with the engine idling.
The variable pitch propeller enables the propeller pitch adaptation to the real boat needs, whose speed
can be accurately kept under control through the engine accelerator fixed positions, thus improving the
fuel consumption rates.
The remarkable size of the hub used on this type of propellers prevents their use at high speeds and
the extremely high cost limits their diffusion.
ENGINE WITH VARIABLE PITCH PROPELLER
1. Clutch - 2. Propeller pitch control.
Propulsion with surface propellers
The surface propellers, different from the traditional ones, are designed to be operated partially under-
water and at high rotation speeds.
The whole propulsion system is applied on the hull stern and the propeller axis exceeds the stern line.
This solution ensures high performances and is adopted mainly on hulls used for speedboat races or
on fast patrol boats. The advantages offered by these propellers are a lack of reduction gears, as the
propeller rotation speed is the same of the engine and the friction reduction due to the lack of hull
protrusions. One of the limits to their diffusion is the difficulty of building propellers able to bear high
stresses at low costs.
DRIVE WITH SURFACE PROPELLERS
MARCH 2004 DRIVE
3.46
MARINE ENGINES INSTALLATION
Figure 13
2 1
Figure 14