Mercury MERCRUISER, Service Manual, Page: 537 / 566

Symptom Cause Solution
3. Steering is stiff and hard to turn,
even when the vessel is not moving.
Steering cylinder pivot
bushings are too tight or
trunnion is bent, causing
mechanical binding.
To test, disconnect the clevis from the steering lever
and turn the steering wheel. If it does not turn easily,
repair trunnion or loosen pivot bushings. Note that
excessively loose connections to a steering cylinder or
steering lever can also cause mechanical binding.
Restrictions in hoses. Find the restrictions and correct them.
Air in hydraulic fluid. Refer to the filling and purging instructions.
The wrong hydraulic fluid
has been used to fill steering
system.
Drain the system and fill with approved hydraulic fluid.
4. The helm unit is bumpy and requires
too many turns from port hard‑over to
starboard hard‑over.
Dirt in inlet check valve of
helm pump.
Replace the helm unit.
5. Steering is easy to turn while
stationary, but becomes hard to turn
when the vessel is underway.
Steering wheel is too small.
Fit a larger wheel, if possible. Refer to the installation
instructions. If the problem cannot be rectified by
changing the steering wheel, proceed with next cause
and solution or consult the factory.
Incorrect setting of trim tabs,
if equipped.
Adjust tabs, if equipped.
6. Drive drifts to port or starboard while
vessel is underway, even when the
wheel is not being turned.
Dirt in check valves.
Remove the check valve plugs. These are the larger
plugs on either side on rear of the helm. Clean the ball
seats and balls, and reassemble.
NOTE: Be prepared to lose a certain amount of
hydraulic fluid during this procedure. Have a small
receptacle available. Refill the system when the check
balls have been reassembled.
7. Turning one steering wheel causes
the second wheel to rotate.
8. Seals will sometimes leak if steering
system is not vented at uppermost
helm.
The helm has a field‑replaceable wheel shaft seal that can readily be replaced by
removing the steering wheel and seal cover held in place by three small screws.
Quad ring No. 210 is supplied in Seastar® Helm Seal Kit HS5151.
9. Vent/fill plug leaks when turning to
port.
Cylinder rod extended during
filling.
Ensure that the cylinder rod is retracted during filling.
Compact Hydraulic Steering
90-8M0099748 eng DECEMBER 2015 © 2016 Mercury Marine Page 8B-11