fountain mercury Express Cruiser 2005, Operation, Maintenance & Warranty Manual

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41
Hull Technology
NEGATIVE TRIM EFFECT
Thrust Angle
+ + + + + +
- - - - - -
CG
FULCRUM
TURNS AT VARIOUS SPEEDS
ASIDE FROM LOW SPEED OPERATION, AND
PARTICULARLY IN BOATS WITH LARGER STEPS,
THERE IS NO REASON TO LOWER THE DRIVES TO LESS
THAN NEUTRAL WHEN TURNING.
REMEMBER, ON A STEP BOTTOM BOAT AT SPEED,
LOWERING THE DRIVES BELOW NEUTRAL CHANGES
THE THRUST ANGLE IN SUCH A WAY AS TO CHANGE
THE PRESSURE ON THE STERN SECTION OF THE BOAT,
CAUSING A LOSS OF ADHESION, AND CREATING AN
UNSTABLE CONDITION THAT IS EXAGGERATED
DRAMATICALLY WHEN TURNING.
WITH THE FULCRUM, OR PIVOT POINT FORWARD OF THE CG, A
VERY UNSTABLE SITUATION IS CREATED. THIS SITUATION
CAN BECOME DISASTEROUS IN A TURN AS THE LEVERAGE
CREATED BETWEEN THE TRANSOM OF THE BOAT AND THE
FULCRUM IS GREATEST.
THIS IS COMBINED WITH THE DECREASED HULL PRESSURE
AFT OF THE CG.
THE RESULT IS AN IMMEDIATE AND VIOLENT TENDANCY TO
SPIN-OUT.