Drive Shaft Propeller and Zincs

January 03, 2016


Propeller       4 V 174 steel shaft


Cutless bearing       5 Aquadrive thrust bearing


PSS shaft seal       6 CV shaft

The propeller must turn at no more than 900 RPM.

The propeller shaft runs parallel to the keel and is in a straight line with the engine, facilitating the alignment and maximising the thrust of the propeller.

The engine power is transmitted to the propeller with an Aquadrive system, where the propeller shaft is aligned to an Aquadrive thrust bearing which absorbs all the propeller thrust and stabilizes the alignment.  From the Aquadrive a constant velocity shaft goes to the gear box of the engine.

The shaft seal is a PSS system, a dripless, maintenance free stuffing box, cooled with engine cooling water.

The propeller shaft is made of V174 steel, with a diameter of 50 mm.  The shaft is supported by two cutless bearings, one on each end.  The propeller shaft runs through a pipe of 70 mm inside diameter.  On the propeller side the pipe consists of a machined piece of aluminum with an outside diameter of 105 mm.


This photograph of the Aquadrive thrust bearing and the PSS shaft seal shows how close they are, thus making for a short length of drive shaft after the second cutless bearing.

The hose that supplies cooling water to the shaft seal (on the right) has not yet been connected.

At the bottom of the shaft seal you can see the two bolts that hold the forward cutless bearing in place.



Taking Out a Propeller Shaft

Hopefully you will never have to pull out a propeller shaft, since due to its location this is quite a chore.  On the other hand the propeller and shaft are completely protected by the hull and it will be extremely unlikely that the shaft will have to be pulled.

Remove the propeller
Remove the CV joint between the engine and aquadrive
Remove the Aquadrive
Detach the exhaust from the engine
Lift the aft part of the engine
Pull out the shaft towards the engine room

Removing a Propeller

To remove a propeller is very simple and straightforward.  Bend back the two wings that lock the propeller nut, unscrew the nut and remove the propeller.



Check the PSS shaft seal for leaks once a week.
Check the wear of the sacrificial zincs regularly and replace if necessary.  Do not forget the ones on the propeller nuts.
Check that all the bolts of the constant velocity joints are tight.

The constant velocity joints are bolted with 16ma bolts, requiring a 24 mm spanner.





Starboard constant velocity joint removed and repainted with epoxy primer and then polyurethane paint.



Haulout at the cantiere LLCampanella, Genova.  Replaced hull and propeller zincs.
  After 2 years in the water fairly corroded, but within the norm.
December Port constant velocity joint removed and repainted by Motonautica Angera.  Checked and found OK.



Haulout at the cantiere LLCampanella, Genova.



Aquadrive Thrust Bearing

The following parts make up an Aquadrive:

A quick calculation gives a shaft torque of app. 1650 Nm, and a thrust of 1480 kg.

The maximum angle permitted for the CV driveshaft is 7degrees, but such an angle shortens the life of the joints due to constant overheating.  Best a maximum angle of 2-3 degrees.  The joint plastic covers at both ends (cuffie) must be treated with care. If they get damaged and the grease leaks out the CV shaft will fail and will have to be replaced.

For engine mounts the original Cummins mounts will be used.

The weight of one Aquadrive thrust bearing is 27 kg.
The Aquadrive thrust bearings were purchased June 2002.
The constant velocity joints were purchased June 2005.



Uni Cardan - Aquadrive thrust bearings Moduline B30/20480, shaft diameter 50 mm


Uni Cardan - Aquadrive constant velocity joints 171378500 length 623 mm


Uni Cardan - Aquadrive adapters for CV joints 12030099 thickness 48 mm

Uni-Cardan Italia spa   
Via Galileo Ferraris, 125
I-20021 Ospiate di Bollate
Phone: +39 02 383 381
Fax: +39 02 333 01030

The following manual provided by the manufacturer is also part of this section:

Uni Cardan AB  Aquadrive Installation Instructions


Propeller Shaft

The propeller shaft, made of V174 steel, has a diameter of 50 mm.  The total length of the shaft is 2565 mm.

The weight of one shaft and nut is 38 kg.


Eliche Radice V174, 50 mm shafts, length 2565 mm.

Eliche Radice S.p.A.
Via Valtellina, 45
20092 Cinisello Balsamo (Mi)
Phone: +39 02 660 49348
Fax: +39 02 612 7688


PSS Shaft Seal

The PSS System is a dripless, maintenance free stuffing box. 
Size for 50 mm shaft and 80 mm OD shaft housing.

The size of the two set screws on each shaft seal is 3/8-16.

Due to the speed of the catamaran of more than 15 kn, the seals are cooled with engine cooling water.






PYI shaft seals  PSS mod. 02-50M-314


Nitrile o rings  

PYI inc,
12532 Beverly Park Road
Lynnwood, WA 98037
Phone: +1 425 355-3669
Fax: +1 425 355-3661

The following manual provided by the manufacturer is also part of this section:

PYI inc PSS shaft seal PSS shaft seal Installation Instructions


Cutless Bearing

The two cutless bearings are made of water lubricated rubber, with the outside pipe made of resin.

Each cutless bearing is held in place by two screws.  The screws of the bearings near the propellers may not be visible due to paint but must be loosened before attempting to remove a bearing.


Eliche Radice Cutless bearings ID 50 mm, OD 70 mm model SCOR

Eliche Radice S.p.A.
Via Valtellina, 45
20092 Cinisello Balsamo (Mi)
Phone: +39 02 660 49348
Fax: +39 02 612 7688



The propellers are made of Mibral and have 4 blades each.  Diameter 690 mm, Pitch 720 mm
Weight 30 kg.

The propeller nut also has a sacrificial zinc to protect the propeller and shaft.

According to Malcolm Tennant a catamaran propeller should have an expanded area ratio of 0.85. 
A usual propeller has a 20% slippage, for a catamaran a slippage of about 15%.

The two propellers calculated and manufactured by Eliche Radice have been remarkably successful.  Whereas the engines are rated for a maximum RPM of 2600 the propellers allow the engines to overspeed only about 50 or 60 RPM, which apparently is well within the norm.



Eliche Radice Mibral 4 blades propellers Otman S8, DS, D 690 mm, P 720 mm, F 50 mm


Eliche Radice bimetal propeller nuts Bimetal, for 50 mm shafts


Eliche Radice propeller nut locks Stainless steel, for 50 mm shafts

Eliche Radice S.p.A.
Via Valtellina, 45
20092 Cinisello Balsamo (Mi)
Phone: +39 02 660 49348
Fax: +39 02 612 7688


Sacrificial Zincs

The main sacrificial zincs are attached to the two keels, in niches to reduce drag.  There are 4 zincs on each side, 8 in total. 
Two paired (one on each side) are attached with 8 ma SS bolts, 70 mm long and autolock nuts.

Two additional sacrificial zincs are attached to the propeller nut.

One zinc is attached to each engine under the right hand side cooling pipe. They are Cummins straight thread.  The head takes a 21 mm spanner and is 24 mm lon. The zinc (minus thread) is 52 mm long and has a diameter of 16 mm.

Sacrificial Zincs


Hull sacrificial zincs 340x60x35 mm, weight 4.6 kg each
distance between the holes 200 mm
2 Propeller nuts zincs od 72 and 53 mm, height 85 mm.
2 Engine zincs 52 mm long and a diameter of 16 mm

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

Polipodio Genova

Tecnoseal Genova.



The Nuts & Bolts of Screws Steve C. D'Antonio, PassageMakerMagazine Vol. 10, No.4,August 2005, p.134


cat_10_e shaft propeller.htm