Multiple Sterndrive Steering Tie Bar Arrangements - Mercury BRAVO Service Manual

SERVICE MANUAL NUMBER 28

Multiple Sterndrive Steering Tie Bar Arrangements

With multiple sterndrives you must select one of several possible steering systems.
Failure to observe the recommended Tie Bar Arrangements as presented in this
section could result in serious damage to the steering and/or trim system compo-
nents. This damage could adversely affect control of the boat.
INTERNAL POWER STEERING WITH INTERNAL TIE BAR ONLY
At the lower end of the performance spectrum, boats not capable of speeds in excess of 60
MPH, the basic internal tie bar is recommended. It connects the slave sterndrive to the stern-
drive that is directly connected to the factory power steering output. This internal tie bar is
available in a variety of lengths from the sterndrive manufacturer.
INTERNAL POWER STEERING WITH INTERNAL AND EXTERNAL TIE BAR
As a boat moves into the moderate performance range of 60-70 MPH or for a reduction in
steering backlash, an external tie bar should be added. External tie bars are usually de-
signed to attach at the aft power trim cylinder bosses. This location is an excellent choice
because of its proximity to the propeller. HOWEVER, because of the potential overstress
that can occur if one drive is trimmed much differently than the other, a dual trim control kit
(Part Number 90362A3) should be installed to limit this potential tilt differential to about 20°.
IMPORTANT: Mercury Marine does not recommend the use of an external tie bar
ONLY with no internal tie bar when using the internal power steering system. This can
cause excessive loads on the steering components on the drive connected to the in-
ternal power steering system. These increased loads can damage the steering com-
ponents, resulting in increased play in the steering of the boat.
EXTERNAL POWER STEERING
When boat speeds move past 70 MPH or if additional steering backlash reduction is desired,
external power steering is recommended. This normally will include an external tie bar
mounted at the same general location as the power steering cylinders, which are generally
attached at the top of the sterndrive's drive shaft housing. With this steering system, no inter-
nal tie bar should be used. These steering cylinders can be attached either inboard (be-
tween) or outboard of the sterndrives.
EXTERNAL POWER STEERING WITH LOW EXTERNAL TIE BAR
For the fastest boats, over 80 MPH, or for the ultimate in steering backlash reduction, use
external power steering, BUT (where mechanically possible) with the external tie bar
mounted at the trim cylinder boss location (as previously described in "Internal Power Steer-
ing with Internal and External Tie Bar" statements). Again, this system does NOT use an
internal tie bar.
90-863160 MAY 2000
CAUTION
POWER STEERING
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