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Section 3 - On The Water
Keep in mind, one of the most important things you can do to help reduce injury or impact damage in these situations is control
the boat speed. Boat speed should be kept to a minimum planing speed when driving in waters known to have underwater
obstacles.
After striking a submerged object, stop the engine as soon as possible and inspect the drive system for any broken or loose
parts. If damage is present or suspected, the power package should be taken to an authorized Mercury MerCruiser dealer for a
thorough inspection and necessary repair.
The boat should be checked for hull fractures, transom fractures, and water leaks.
Operating with damaged underwater drive components, rudder, or boat bottom could cause additional damage to other parts of
the power package, or could affect control of the boat. If continued operation is necessary, do so at greatly reduced speeds.
Operating a boat or engine with impact damage can result in product damage, serious injury, or death. If the vessel
experiences any form of impact, have an authorized Mercury Marine dealer inspect and repair the vessel or power package.
Conditions Affecting Operation
Weight Distribution (Passengers and Gear) Inside the Boat
Shifting weight to rear (stern):
•
Generally increases speed and engine RPM
•
Causes bow to bounce in choppy water
•
Increases danger of following wave splashing into the boat when coming off plane
•
At extremes, can cause the boat to porpoise
Shifting weight to front (bow):
•
Improves ease of planing
•
Improves rough water ride
•
At extremes, can cause the boat to veer back and forth (bow steer)
The Bottom of the Boat
To maintain maximum speed, the boat bottom should be:
•
Clean, free of barnacles and marine growth
•
Free of distortion; nearly flat where it contacts the water
•
Straight and smooth, fore and aft
Marine vegetation may accumulate when the boat is docked. This growth must be removed before operation; it may clog the
water inlets and cause 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
Elevation and Climate
Elevation and climate changes will affect the performance of your power package. Loss of performance can be caused by:
•
Higher elevations
•
Higher temperatures
•
Low barometric pressures
•
High humidity
For you to have optimum engine performance under changing weather conditions, it is essential that the engine be propped to
allow the engine to operate at or near the top end of the specified maximum RPM range with a normal boat load during your
normal boating weather conditions.
In most cases, recommended RPM can be achieved by changing to a lower pitch propeller.
Page 32
WARNING
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90-8M0086943
DECEMBER 2014
eng
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