Conventional steering of the vessel is achieved through controlling the flow of oil through hydraulic 

cylinders attached to a tiller. How the flow is controlled determines the type of steering system. 




In a single speed system a direct acting hydraulic valve is commanded open or closed to control the flow of oil to the cylinders and rudder consequently movement. The most economical choice, single speed control is traditionally used on smaller systems where hydraulic shock resulting from the rapid starting and stopping of oil flow is not an issue.


EMI designed systems use softshift valves to greatly minimize hydraulic shock and reduce wear on mechanical components.


Features / Benefits:


  • Economical

  • Simple

  • Reliable

  • Soft Shift Valves 



In a dual speed system, a second valve is employed to initially allow only about half the flow of oil to the cylinders. Once rudder movement begins, full flow is allowed to move the rudder at full speed. Similarly, as the commanded position is about to be reached, flow is before completely stopping flow and rudder movement. Hydraulic shock is minimized using this steering method with only a moderate increase in cost or complexity.


EMI has installed over 50 systems of this type on larger supply boats and tugs including the largest 

towboat operating on the inland waterways, the US Army Corp of Engineers towboat, M/V Mississippi.


Features / Benefits:


  •  Smoother operation than single speed

  •  Accommodates larger system flows without introducing substantial levels of hydraulic shock. 

  •  Initial system costs more economical than Proportional Steering



In this type of system the amount of oil directed to the cylinders is ramped from zero to full flow using a proportional valve. The amount of oil can be controlled over the entire flow range resulting in virtual elimination of hydraulic shock. Consequently, life expectancy of hoses, cylinders and jockey bar connecting pins is greatly increased. 


Additionally, with proportional systems horse-power limiting design features can be implemented which reduce the pump and motor size requirements. With this decrease in size, reductions in generator power requirements of up to 50% have be realized. While more expensive than the alternatives, the life cycle costs and inherent reliability improvements are driving many customers to this type of system. 


Features / Benefits:


  • Elimination of hydraulic shock

  • Smooth steering operation

  • Increased life expectancy of steering system components

  • Reduction in steering system power requirements








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