Section 3 - On the Water
90-866938081 MAY 2009 Page 31
Zeus Drive Alignment
The Zeus Drives are aligned by the boat manufacturer, and must not be adjusted by anyone
other than your Cummins MerCruiser Diesel Authorized Service and Repair Facility. The
Zeus drives automatically recalibrate to this setting at each startup. The drives do not need
to be re‑aligned under normal use.
Conditions Affecting Boat Operation
Weight Distribution (Passengers and Gear) Inside the Boat
Shifting weight to the rear (stern):
• Causes the bow to bounce in choppy water.
• Increases the danger of a following wave splashing into the boat when coming off
plane.
• Can cause the boat to porpoise at extremes.
Shifting weight to the front (bow):
• Improves ease of planing.
• Improves rough water ride.
• Can cause the boat to veer back and forth (bow steer) at extremes.
Bottom Of Boat
To maintain maximum speed, the boat bottom should be:
• Clean and free of barnacles and marine growth.
• Straight and smooth (fore and aft).
Marine vegetation can accumulate when the boat is docked. Remove this growth before
operation; it can clog the water inlets and outlets, causing the engine to overheat.
Cavitation
Cavitation occurs when water flow cannot follow the contour of a fast‑moving underwater
object, such as a gear housing or a propeller. Cavitation increases propeller speed while
reducing boat speed. Cavitation can seriously erode the surface of the gear housing or the
propeller. Common causes of cavitation are:
• Weeds or other debris snagged on the propeller
• Bent propeller blade
• Raised burrs or sharp edges on the propeller
Ventilation
Ventilation is caused by surface air or exhaust gases that are introduced around the
propeller resulting in propeller speed‑up and a reduction in boat speed. Air bubbles strike
the propeller blade and cause erosion of the blade surface. If allowed to continue, eventual
blade failure (breakage) will occur. Excessive ventilation is usually caused by:
• A missing propeller diffuser ring.
• A damaged propeller or gear housing, which allows exhaust gases to escape between
propeller and gear housing.
Propeller Selection
IMPORTANT: The installed propellers must allow the engine to reach engine Rated Speed
(RPM) with the boat fully loaded and with all customer stores on board. With the boat less
than fully loaded the engines should reach engine Rated Speed (RPM) with less than a
100% load. Use the VesselView display to verify engine RPM and percent load.
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