Impact With Underwater Hazards; Conditions Affecting Operation; Weight Distribution (Passengers And Gear) Inside The Boat; Bottom Of Boat - Mercury TDI 3.0L Owner's Operation And Maintenance Manual

There is another less common hazardous result from allowing your boat to launch off of a wave or wake. If the bow of your boat
pitches down far enough while airborne, upon water contact it may penetrate under the water surface and submarine for an
instant. This will bring the boat nearly to a stop in an instant and can send the occupants flying forward. The boat may also veer
sharply to one side.

Impact with Underwater Hazards

Reduce speed and proceed with caution when operating in shallow water or in areas where the waters are suspected of having
underwater obstacles that could be struck by the drive components, rudder, or the boat bottom.
IMPORTANT: To help reduce injury or impact damage from striking a floating or underwater object, control the boat speed.
Under these conditions, boat speed should be kept to a maximum of 24 to 40 km/h (15 to 25 mph).
The following demonstrate some, but not all, examples of what can happen if the boat strikes an object:
• The boat could move suddenly in a new direction. A sharp change in direction or turn can throw occupants out of their
seats or out of the boat.
• A rapid reduction in speed. This will cause occupants to be thrown forward, even out of the boat.
• Impact damage to the underwater drive components, rudder, or boat.
Keep in mind that 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 a Mercury Diesel‑authorized repair facility for a
thorough inspection and any necessary repair.
The boat should be checked for hull fractures, transom fractures, and water leaks.
Operating with damaged drive components, rudder, or boat bottom could cause 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 the 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 the front (bow):
• Improves ease of planing
• Improves rough‑water ride
• At extremes, can cause the boat to veer back and forth (bow steer)

Bottom of Boat

To maintain maximum speed, ensure that the boat bottom is:
• Clean, free of barnacles and marine growth
• Free of distortion, nearly flat where it contacts water
90-8M0145546 MAY 2018
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Section 2 - On The Water
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