Hydraulic FAQs (Cont.)
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FREQUENTLY ASKED QUESTIONS
I notice that unbalanced cylinders (like the HC5370-3 outboard side mount) have a
different number of turns to hard over in each direction. Why is this so?
The answer is in the design of an unbalanced cylinder.
When the helm is turned one turn, a certain volume of fluid is pumped into the cylinder.
On one side of an unbalanced cylinder piston is a rod, which reduces the effective cylinder volume.
The cylinder area on the other side of the piston has no rod, thus more volume available for fluid pumped
in from the helm.
The piston side with the rod will move farther per turn of the wheel (less turns to hard over) because less
space is available for the fluid than the side with no rod.
A balanced cylinder has a rod on each side of the piston and will move equally to either side per wheel
turn to that side.
(See diagrams below.)
FLUID CROSS-SECTION
RIGHT
TURN
more volume available - less
rod movement per wheel turn
FLUID CROSS-SECTION
LEFT
TURN
less volume available - more
rod movement per wheel turn
UNBALANCED CYLINDER:
FLUID CROSS-SECTION
RIGHT
TURN
equal volume available - equal
rod movement per wheel turn
FLUID CROSS-SECTION
LEFT
TURN
equal volume available - equal
rod movement per wheel turn
BALANCED CYLINDER:
I am upgrading to SeaStar steering, but have discovered that the new helm won’t
cover the holes left by the old one. What should I do?
That depends on what was in the boat originally:
a. If you are upgrading from SeaStar Solutions rotary mechanical steering (Safe-T, Big-T or rotary NFB),
pre-1991 SeaStar (with square mounting flange) or SyTen, you will need to purchase a HA5418 Back
Plate Kit. This will cover the old holes and provide extra dash rigidity.
b. If you are upgrading from SeaStar Solutions' Rack & Pinion or Morse® mechanical steering, you will
have to enlarge the dash holes to accommodate the new helm. You may also need to purchase the
HA5405 Backing Ring Kit to increase dash rigidity.
STEERING - FAQ (Hydraulic)
