Water Testing - Mercury Jet 25 Manual

BOATS WITH A FLAT BOTTOM HULL
1. Place (center) the outboard on the boat transom. Set the
height of the outboard on the boat transom so that the front
edge of the water intake housing is in line with the bottom of
the boat as shown. Fasten outboard to the transom at this
height.

Water Testing

CHECKING FOR CAVITATION
The initial outboard height setting should be close to the optimum
setting for the outboard. However, because of the hull design of
some boats, obstructions, or imperfections in the hull ahead of the
water intake, adjustments may be required to prevent cavitation at
running speeds.
When operating the boat, the outboard driveshaft housing should
be vertical, or tilted toward the boat, when planing to provide a
scooping angle on the water intake. Tilting the outboard out beyond
a vertical position reduces the scoop angle and can cause impeller
slippage and cavitation.
IMPORTANT: If the angle of the boat transom does not allow the
driveshaft housing to be positioned vertical, a wedge kit should be
installed behind the transom brackets to increase the tilt‑in angle.
NOTE: Slight cavitation in sharp turns and rough water is
acceptable, but excessive cavitation is harmful to the outboard and
should be avoided.
Test run the boat. If cavitation occurs (air enters the pump), the
first thing to try is lowering the outboard mounting height.
ENGINE INSTALLATION
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