Steering Mechanism

January 16, 2016

                      Steering mechanism

The steering mechanism of the PH8 is hydraulic.

An electro hydraulic pump unit controlled by joystick on the bridge or by the MicroCommander handheld remote control provides the necessary hydraulic pressure to the two rudder actuators.

The manual pump unit powered by the steering wheel on the bridge is only for emergencies.  The torque required to rotate the rudder stock is approximately 2.15 kNm.

A rudder position indicator on the bridge graphically displays the rudder position of the starboard rudder. The power for the display comes from the starboard engine DC power.


Port rudder tiller compartment.

The Rule float switch on the upper right only gives an alarm since no pump is connected to it.

The rudder position is supplied to the Raymarine autopilot by a Raymarine sensor mounted next to the port rudder.

The electro hydraulic pump is in the engine room entrance compartment of the starboard hull and is powered by a breaker on the starboard hull panel.

During navigation the pump is always on and two electro valves on the pump open the oil flow to turn right or left.  A small panel in the starboard hull, behind the hull panel contains the three relays to operate the pump.  One mechanical relay turns on the pump and two electronic relays power the valves to go right or left.

All the hydraulic piping is stainless steel and hydraulic rubber hoses.

The autopilot is described in the electronics section.

The following manual provided by Marsili, the steering equipment manufacturer is also part of this section:

Marsili Aldo & C. Marsili Manual

Marsili Aldo & C. sas
Via N. Bixio, 63
I-62012 Civitanova Marche (MC)
Phone: +39 0733 813 977
Fax: +39 0733 771 284


Before Starting

Make sure that the circuit breaker for the electro hydraulic pump is on. It is located in the starboard hull panel.
To test the steering turn on the hydraulic pump with the switch on the bridge.  The red LED beside the joystick must come on.
Press the right and left button.  The two LEDs that indicate current to the hydraulic fluid valves must light.
Check that the rudders actually move by turning on the starboard engine key and watch the rudder angle indicator.

Synchronization of the Rudders

Since the two rudders are completely independent from each other it is possible that they go out of synchronization, that is, they are no longer parallel to each other.  In that case turn the rudders completely to one side and they will be synchronized again.

Disabling The Steering

The steering can be completely disabled so that you cannot turn anymore the rudders nor with the manual wheel or the autopilot by opening the bypass valve located near the electro hydraulic pump.  You can use this feature as a anti-theft device, but do not forget to close the bypass valve before starting the engines!

Loss of Steering

A complete loss of steering could happen if a hydraulic line bursts, with the consequent loss of hydraulic fluid.  In an emergency the boat can be steered using differential power on the engines.

Filling and Bleeding the Empty Hydraulic Lines

Use only hydraulic oil with the following properties:

Engler viscosity 1.8 - 2.5 E at a temperature of 40 C.

AGIP OSO 15 IP IP Hydrus OIL 10
BP Energol HP 10 Q8 HAYDN 10
CASTOL Hyspin AVS 10 SHELL Tellus OIL C10

To fill the hydraulic lines unscrew a bleeding valve on the rudder actuator and replace the valve with a piece of plastic hose ending in a bucket to collect the surplus oil.

Fill the hand pump unit on the bridge from the filling cap then turn the steering wheel to the left until the oil reaches the level of the upper sight glass.  Repeat until all the air has been eliminated and then close the bleeding valve.  Turn the steering wheel in the other direction to fill and bleed the other side.  To help bleed the lines open the bypass valve located near the electro hydraulic pump.

Then fill the electro hydraulic unit up to a few centimeters below the filling cap, on top of the hydraulic oil tank. 

Once the system is full of oil turn the rudder from side to side and check that there are no oil leaks anywhere.  

To completely fill the hydraulic steering system takes approximately 16 l of hydraulic oil.

Bleeding Hydraulic Lines

If the steering becomes "mushy", it is caused by air bubbles trapped in the hydraulic lines or by a lack of hydraulic oil. Check the hydraulic oil level and add oil if necessary, proceeding like when filling the empty hydraulic lines.



Before each trip or every week check the hydraulic oil level at the hand pump unit and the autopilot unit.  At the hand pump the oil level must not be lower than the upper sight glass.  The level of the electro hydraulic unit must be up to a few centimeters below the filling cap.

Every three months grease the two rudder actuators at their greasing nipples.  Also make sure that the parts of the actuators that are not stainless steel are protected by a film of grease.

Every three months check that there are no oil leaks anywhere in the system.  Especially check both ends of the rubber hoses of the rudder actuators.  




The joystick on the bridge is the main steering devices for the cat.

To operate the steering the electro hydraulic pump must be turned on.  (See the procedures, before starting check lists.)

Another way to steer is to use the MicroCommander handheld control and move the switch on the botton to the right or left.


handheld open

To operate the MicroCommander handheld control the electro hydraulic pump must be on.  (See below and the before starting check lists.) The MicroCommander power must be on by turning on at least one of the engine switches.  It is not necessary to take control with the handheld to operate the rudder.  In other words, whenever the electro hydraulic pump is turned on, the steering switch is active.

When steering to the right or to the left two small lights on the instrument panel, a green one (turning to starboard and a red one, turning to port) light up.

If there is a problem with the steering switch on the MicroCommander handheld control but the joystick operates correctly check that the four fastons in the remote relay junction box make good contact.  The steering switch on the handheld control is a straight electrical connection to the two electronic relays in the small panel in the starboard hull.  There is no electronics in between.  Even when the safety device on the back of the handheld control is out the steering must work.


The MicroCommander handheld control is featured in the Engine, Engine Controls and Exhaust section.


Vetus joystick EHP JST

Vetus Italia srl
Via Palandri, 41
I-50050 Limite sull'Arno (FI)
Phone: +39 0571 57122
Fax: +39 0571 578143


Rudder Angle Indicator and Sensors

There are two rudder angle sensors, one for each rudder.

The Marsili starboard rudder angle sensor provides the rudder position to a rudder angle indicator on the bridge.

The rudder angle indicator is powered by the starboard auxiliary key on circuit, that is it automatically gets power when turning on the starboard engine switch.

The Raymarine port rudder angle sensor provides the rudder position to the autopilot.

< td width="180">TAB /U/M + IAB /03


Raymarine rudder angle sensor(port)  


Marsili rudder angle sensor(starboard)


San Giorgio S.E.I.N. master rudder angle indicator  

San Giorgio S.E.I.N.
I-16100 Genova




The relay to turn on and off the hydraulic pump is electro mechanical. 
Cole Hersee continuous duty 85A, insulated, plasticized.  Copper contact terminals, 5/16",-24 thread.
Purchased March 2007.

The two relays that open the valves to turn right and left are electronic ones.
Cole Hersee ultra-reliable electronic solenoids.

Purchased April 2005

stbd relays

All three relays are located in the steering panel in the starboard hull.


Cole Hersee solenoid, continuous duty 24117-01BP


Cole Hersee ultra reliable electronic solenoids Cole Hersee 48785


Electro Hydraulic Pump

The electro hydraulic pump is located in the starboard room before the engine room, close to the bypass valve.

The breaker to turn on the electro hydraulic pump and activate the joystick is located in the starboard branch circuit panel.   

Electric motor, 12V, 2700 RPM, 32A, 0.3kW  MP/0306159, Tipo MP71S/2B5
Gianneschi e Ramaciotti, Capezzano Pianore (LU)

The two electro valves draw app. 6 A each when energized by the autopilot or the joy stick.

The hydraulic oil tank next to the electric motor must be filled up to a few centimeters below the filling cap.

A set of valves permits the removal of the electro hydraulic pump unit without having to empty the hydraulic oil lines.


Marsili electro Hydraulic pump (centralina) Marsili CC - 075


Steering Wheel Pump

The manual hydraulic pump on the bridge is an emergency unit, since normally the joystick is used.

The pump must be filled with hydraulic oil up to the uppere sight glass.


Marsili manual hydraulic pump Marsili C 7/55; C 7/80


Rudder Actuator

Two hydraulic actuators power the two tiller arms.


Marsili hydraulic actuators Marsili CL 0-80/100/R


Hydraulic Piping and Fittings

All hydraulic hoses used for the hydraulic steering are hydraulic hoses connected to the stainless steel pipes with conical hydraulic fittings.

The piping is stainless steel, with stainless steel fittings.



Sked hung rudder, with a 316 stainless steel stock of 75 mm and a laminated foam blade covered with glass fiber.
Acetal (Delrin ) plastic is used for the bearings of the rudder stock and to provide isolation of the SS from the alloy.  A set of rubber o-rings make the assembly water tight.

Rudder depth (from the bottom of the aft flat) 1100 mm, chord 650 mm, rudder section 12.3% series NACA section.

The distance between the rudders is approximately 5020 mm.


cat_13_e steering.htm