Hydraulic & Manual Steering
Systems Selection Guide & Tips

 

Hydraulic Steering Systems consist of three basic main components:

1. The Helm Pump
2. The Cylinder
3. The Hose or Tubing (to connect the cylinder to the helm pump)

To select the type of cylinder and the size of the helm best suited to your boat, take into consideration the following variables:

1. Type of boat (planning or displacement)
2. Type of engine (outboard, Inboard, sterndrive)
3. Number of engines
4. Total power of the engines
5. Space available in the splashwell and dash areas for the steering components

When making your choice, specify the following options:

1. Number of steering stations
2. Additional features such as autopilots

Number of Turns in Relation to Steering Effort

When choosing the responsiveness of a steering system, remember that the steering wheel effort is proportional to the number of wheel turns: the quicker the steering, the harder the effort.

The number of wheel turns lock to lock depends on the volume of the cylinder and the displacement of the helm.

Other factors that can influence steering effort are the vessel speed, rudder size and hull type.

How to Calculate Rudder Torque

When the torque necessary to maneuver a boat was not specified neither by a naval architect nor by the shipbuilder yard, it can be calculated.

It must be known that the torque necessary to maneuver a boat depends on:

Speed of the water flowing on the surface of the rudder at a certain angle. Rudder size Total sweep of rudder (and part of the boat) when rudder shaft not perpendicularCompensating surface

 

Torque calculation for maxi speed about 25 knots:

T = S x [( 0,4 a ) - b] x V2 x k
T = Torque
S = Total surface of the rudder in m2 ( h x a )
h = Height of the rudder in m
a = Width of rudder in m
b = The value of the compensation in m
V = Speed of the boat on knots
k = Coefficient according to the total angle of the rudder

- Port to starboard 70     k = 15,89
- Port to starboard 80     k = 17,80
- Port to starboard 90     k = 19,52

Straightening according to the type of boats:

• For Boats equipped with Jet Engines Tx1,3
• For power boats w/2 engines & 1 rudder Tx 0,5
• For sail boats Tx 0,5

Outboard Steering Front Mount and Side Mount Cylinders Application Guide
Engine Manufacturer	Year	Model	Hydraflex OB Cylinder
			Engine without powersteering	Engine with powersteering
Johnson & Evinrude	1977   1990 1991 to date 1991 to date 1991 to date 1977   1990 1991 to date 1991 to date	90 - 300 hp   90 - 225 hp 150 - 175 hp 250 - 300 hp   65 - 155 hp 100 - 155 hp   80 - 105 hp	OB-BFM or OB-SM	OB-SM* *see note 1
OMC-Seadrive	1984 to date	1.6 litre	OB-BFM or OB-SM * * see note 2
Mercury & Mariner	1984 only 1984 only 1985   1988 1989 only 1989 only 1990 only 1991 to date	150 - 200 hp   90 - 155 hp 115 - 220 hp 100 - 115 hp 135 - 250 hp   75 - 250 hp   75 - 275 hp	OB-BFM or OB-SM
Suzuki	1986 to date 1990 to date	150 - 220 hp 100 hp	OB-BFM or OB-SM
Yamaha	1984 - 1985 1986 only 1987 to date 1990 to date 1989 to date 1990 to date	115 - 220 hp 115 - 220 hp 115 - 220 hp 220 hp  70 - 90 hp   80 - 140 hp	OB-BFM or OB-SM
Tohatsu	1990 to date	120 - 140 hp	OB-BFM or OB-SM
Force	1985 to date	90 - 150 hp	OB-BFM or OB-SM

Note 1: If the OMC input cylinder (ref. OMC P.No. 985519) is fitted, an adaptor fitting is required (ref. Parker P.No. F6X-S 10-3/8").

Note 2: Multiple OMC Seadrive installation require the OMC sychronization valve (ref. OMC P.No. 983430).

Outboard Steering Front Mount Cylinder Order Guide
System Description	Components	Model	Quantity
Single Engine Single Cylinder Wheel turns: 5,4 Applications up to 300 hp max	Front Mount Cylinder Hydra Helm Pump Hose Kit Oil for additional station: Hydra Helm Pump Fitting Kit Hose Kit Oil	OB - BFM LD 25 Kit OB Oil 22       LD 25 Kit OB - 2S Kit OB Oil 22	1 1 1 3 1    1 1 1 1 1
Dual Engine Single Cylinder Wheel turns: 3,8 Application: up to 450 hp max (non-counter rotating engine) Application: up to 600 hp max (counter rotating engine)	Front Mount Cylinder Hydra Helm Pump Hose Kit Oil Tie Bar for additional station: Hydra Helm Pump Fitting Kit Hose Kit Oil	OB - BFM LD 35 Kit OB Oil 22 Supplied by eng. manuf.       LD 35 Kit OB - 2S Kit OB Oil 22	1 1 1 3    1      1 1 1 1 1
Dual Engine Dual Cylinder Wheel turns: 6,3 Application: up to 600 hp max (non-counter rotating engine) Application: all counter rotating engine	Front Mount Cylinder Hydra Helm Pump Hose Kit Tee Fitting Kit Oil Tie Bar for additional station: Hydra Helm Pump Fitting Kit Hose Kit Oil	OB - BFM LD 42 Kit OB Standard Oil 22 Supplied by eng. manuf.       LD 42 Kit OB - 2S Kit OB Oil 22	2 1 2 1 3    1    1 1 1 1 1

Warning: The OB-BFM front mount cylinder is not recommended for use in installations where the boat speed exceeds 65 mph (65 knots) and the power exceed max Coast Guard or M.O.T. recommendation for the boat.

Outboard Steering Side Mount Cylinder Order Guide
System Description	Components	Model	Quantity
Single Engine Single Cylinder Wheel turns: 5,4/ 6,6 Applications up to 300 hp max	Front Mount Cylinder Hydra Helm Pump Hose Kit Oil for additional station: Hydra Helm Pump Fitting Kit Hose Kit Oil	OB - SM LD 25 Kit OB Oil 22       LD 25 Kit OB - 2S Kit OB Oil 22	1 1 1 3 1    1 1 1 1
Dual Engine Single Cylinder Wheel turns: 3,7/4,6 Application: up to 300 hp max (non-counter rotating engine) Application: up to 600 hp max (counter rotating engine)	Front Mount Cylinder Hydra Helm Pump Hose Kit Oil Tie Bar for additional station: Hydra Helm Pump Fitting Kit Hose Kit Oil	OB - SM LD 35 Kit OB Oil 22 Supplied by eng. manuf.       LD 35 Kit OB - 2S Kit OB Oil 22	1 1 1 3    1      1 1 1 1
Dual Engine Dual Cylinder Wheel turns: 6,2/7,7 Application: up to 600 hp max (non-counter rotating engine) Application: all counter rotating engine	Front Mount Cylinder Hydra Helm Pump Hose Kit Tee Fitting Kit Oil Tie Bar for additional station: Hydra Helm Pump Fitting Kit Hose Kit Oil	OB - SM LD 42 Kit OB Standard Oil 22 Supplied by eng. manuf.       LD 42 Kit OB - 2S Kit OB Oil 22	2 1 2 1 3    1    1 1 1 1

Inboard 116 Cylinder Application - Torque Up To 58 kgm - 5,043 lbs. in.
Hull Type	Boat Length Up To	Configuration	Boat	Hydraflex System
Planing	28 ft. (8,50 m)	Single Engine - Single or dual station	Pleasure	1
			Work	1
	30 ft. (9,10 m)	Twin Engine - Single or dual station	Pleasure	1
			Work	1
Displacement	28 ft. (8,50 m)	Single Engine - Single or dual station	Pleasure	1
			Work	1
	30 ft. (9,10 m)	Twin Engine - Single or dual station	Pleasure	1
			Work	1

Inboard 173 Cylinder Application - Torque Up To 87 kgm - 7,565 lbs. in.
Hull Type	Boat Length Up To	Configuration	Boat	Hydraflex System
Planing	38 ft. (11,60 m)	Single Engine - Single or dual station	Pleasure	2 - 3
			Work	3
	44 ft. (13,40 m)	Twin Engine - Single or dual station	Pleasure	2 - 3
			Work	3
Displacement	32 ft. (9,70 m)	Single Engine - Single or dual station	Pleasure	2 - 3
			Work	3
	38 ft. (11,60 m)	Twin Engine - Single or dual station	Pleasure	2 - 3
			Work	3

Inboard 222 Cylinder Application - Torque Up To 111 kgm - 9,652 lbs. in.
Hull Type	Boat Length Up To	Configuration	Boat	Hydraflex System
Planing	44 ft. (13,40 m)	Single Engine - Single or dual station	Pleasure	4 - 5
			Work	5
	50 ft. (15,20 m)	Twin Engine - Single or dual station	Pleasure	4 - 5
			Work	5
Displacement	38 ft. (11,60 m)	Single Engine - Single or dual station	Pleasure	4 - 5
			Work	5
	44 ft. (13,40 m)	Twin Engine - Single or dual station	Pleasure	4 - 5
			Work	5

Inboard 293 Cylinder Application - Torque Up To 147 kgm - 12,782 lbs. in.
Hull Type	Boat Length Up To	Configuration	Boat	Hydraflex System
Planing	57 ft. (17,40 m)	Single Engine - Single or dual station	Pleasure	6
			Work	6
	60 ft. (18,30 m)	Twin Engine - Single or dual station	Pleasure	6
			Work	6
Displacement	57 ft. (17,40 m)	Single Engine - Single or dual station	Pleasure	6
			Work	6
	60 ft. (18,30 m)	Twin Engine - Single or dual station	Pleasure	6
			Work	6

Inboard 378 Cylinder Application - Torque Up To 188 kgm - 16,347 lbs. in.
Hull Type	Boat Length Up To	Configuration	Boat	Hydraflex System
Planing	62 ft. (18,90 m)	Single Engine - Single or dual station	Pleasure	7
			Work	7
	65 ft. (19,80 m)	Twin Engine - Single or dual station	Pleasure	7
			Work	7
Displacement	62 ft. (18,90 m)	Single Engine - Single or dual station	Pleasure	7
			Work	7
	65 ft. (19,80 m)	Twin Engine - Single or dual station	Pleasure	7
			Work	7

Inboard 648 Cylinder Application - Torque Up To 327 kgm - 28,486 lbs. in.
Hull Type	Boat Length Up To	Configuration	Boat	Hydraflex System
Planing	69 ft. (21 m)	Single Engine - Single or dual station	Pleasure	8
			Pleasure	8
	70 ft. (21,40 m)	Twin Engine - Single or dual station	Pleasure	8
			Work	8
Displacement	69 ft. (21 m)	Single Engine - Single or dual station	Pleasure	8
			Work	8
	70 ft. (21,40 m)	Twin Engine - Single or dual station	Pleasure	8
			Work	8

LD Series Inboard Steering Order Guide

 

Sist. 1 Maximum rudder torque 58 kgm - 5,043 lbs. in. Turns lock to lock 4.6 Components Model Quantity Hydra Helm Pump Cylinder 3/8' Nylon Tube Oil    for additional station: Hydra Helm Pump Fitting Kit Oil Extra Tube LD 25 I-B 116 TU 95 Oil 22            LD 25 Kit 95-2S Oil 22 TU 95 1 1 on request 3       1 1 1 on request

Sist. 2 Maximum rudder torque 87 kgm - 7,565 lbs. in. Turns lock to lock 6.9 Components Model Quantity Hydra Helm Pump Cylinder 3/8' Nylon Tube Oil    for additional station: Hydra Helm Pump Fitting Kit Oil Extra Tube LD 25 I-B 173 TU 95 Oil 22            LD 25 Kit 95-2S Oil 22 TU 95 1 1 on request 3       1 1 1 on request

 

Note: 1) For systems 3, 4 and 5, 5/16" nylon tubing can be used as an alternative to the standard 3/8" tubing for plumbing the system. These applications must be specified when ordering. Sist. 5 Maximum rudder torque 111 kgm - 9,652 lbs. in. Turns lock to lock 5.2 Components Model Quantity Hydra Helm Pump Cylinder 3/8' Nylon Tube Oil    for additional station: Hydra Helm Pump Fitting Kit Oil Extra Tube LD 25 I-B 116 TU 95 Oil 22            LD 25 Kit 95-2S Oil 22 TU 95 1 1 on request 3       1 1 1 on request 2) For systems 1, 2, 3, 4 and 5 copper tubing (3/8" dia. or 10 mm dia.) can be used as an alternative tubing for plumbing the system. For these qualifications.

 

HD Series Inboard Steering Order Guide

 

Sist. 6 Maximum rudder torque 147 kgm - 12,782 lbs. in. Turns lock to lock 4.6 Components Model Quantity Hydra Helm Pump Cylinder Valve & Fitting Kit    Oil Copper Tube    for additional station: Hydra Helm Pump Fitting Kit Oil HD 63 I-B 293 Kit120-metric Kit127-Amer. Oil 22 12 mm or 1/2"         HD 63 Kit120-2S-metri Kit127-2S-Amer. Oil 22    1 1 1 1 3    1 1 1 1 1

Sist. 7 Maximum rudder torque 188 kgm - 16,347 lbs. in. Turns lock to lock 6 Components Model Quantity Hydra Helm Pump Cylinder Valve & Fitting Kit    Oil Copper Tube l    for additional station: Hydra Helm Pump Fitting Kit Oil HD 63 I-B 378 Kit120-metric Kit127-Amer. Oil 22 12 mm or 1/2"         HD 63 Kit120-2S-metri Kit127-2S-Amer. Oil 22    1 1 1 1 3    1 1 1 1 1

 

Sist. 8	Maximum rudder torque 327 kgm - 28,486 lbs. in.		Turns lock to lock 10.2
Components		Model	Quantity
Hydra Helm Pump Cylinder Valve & Fitting Kit    Oil Copper Tube    for additional station: Hydra Helm Pump Fitting Kit Oil		HD 63 I-B 648 Kit120-metric Kit127-Amer. Oil 22 12 mm or 1/2"            HD 63 Kit120-2S-metri Kit127-2S-Amer. Oil 22	1 1 1 1 3       1 1 1 1 1

 

Sterndrive Application Guide

 

Engine Manufacturer	Year	Model	Hydraflex IO Cylinder
			Non power assist engine	Power assist engine
BMW	To date	All	UC-133IOL	UC-133IOL
Mercruiser	1983 & prior 1984 to date 1984 to date 1984 to date	Mercruiser I Alpha I Bravo I Bravo II	UC-B133IOL UC-B133IOB* UC-B133IOB* UC-B133IOB* * Requires the Quicksilver clevis (P. No. B98735A1)	UC-133IOL UC-133IOL UC-133IOL UC-133IOL
OMC	1985 & prior 1986 to date 1986 to date	400/800 series Cobra King Cobra	N/A UC-B133IOB* UC-B133IOB* * Requires an adapter supplied by engine manufacturer	N/A UC-133IOS UC-133IOS
Volvo	To date To date To date To date 1992	275 280 290 Diesel All	UC-133IOB UC-133IOL UC-133IOL UC-215-1	UC-133IOL UC-133IOL UC-133IOL UC-133IOL UC-133IOL
Yamaha	1989 to date	All	N/A	UC-133IOL

Note: These recommendations should be used a general reference only and apply to factory stock sterndrives only.

Maximum rudder torque 66 kgm - 5,739 lbs. in. Turns lock to lock Bal. 5,3  Unb. 5,3/6,5 Components Model Qty. Hydra Helm Pump Cylinder 3/8" Nylon Tube Oil    for additional station: Hydra Helm Pump Fitting Kit Oil Extra Tube LD 25 see appl. list TU 95 Oil 22            LD 25 Kit95-2S Oil 22 TU 95    1 1  on request 3 1       1 1 1 on request 1

Maximum rudder torque 66 kgm - 5,739 lbs. in. Turns lock to lock Bal. 3,8  Unb. 4,7/5,3 Components Model Qty. Hydra Helm Pump Cylinder   3/8" Nylon Tube Oil    for additional station: Hydra Helm Pump Fitting Kit Oil Extra Tube LD 35 see appl. list TU 95 Oil 22         LD 35 Kit95-2S Oil 22 TU 95    1 1 on request 3       1 1 1 on request 1

Note: 3/8" or 10 m dia. copper tubing can be used as an alternative tubing for plumbing the system. For these applications a fitting kit - Kit 95 or Kit 100 - is required.

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