Mercury Avator 7.5e Operation, Maintenance And Installation Manual page 24

BOTTOM OF BOAT
For maximum speed, the bottom of the boat should be nearly a flat plane
where it contacts the water and particularly straight and smooth in fore and aft
direction.
•
Hook: Hook exists when the bottom of the boat is concave in the fore
and aft direction when viewed from the side. When the boat is planing,
hook causes more lift on the bottom near the transom and allows the bow
to drop, greatly increasing wetted surface and reducing the boat speed.
Hook frequently is caused by supporting the boat too far ahead of the
transom while hauling on a trailer or during storage.
• Rocker: Rocker exists if the bottom of the boat is convex in the fore
and aft direction when viewed from the side, and the boat has a strong
tendency to porpoise.
• Surface roughness: Moss, barnacles, etc., on boat or corrosion of the
outboard's motor lower unit housing increases surface friction and can
cause speed loss. Clean surfaces when necessary.
WATER ABSORPTION
It is imperative that all through‑the‑hull fasteners be coated with a quality
marine sealer at time of installation. Water intrusion into the transom
core and/or inner hull will result in additional boat weight (reduced boat
performance), hull decay, and eventual structural failure.
CAVITATION
Cavitation occurs when water flow cannot follow the contour of a fast‑moving
underwater object, such as an outboard lower unit housing or a propeller.
Cavitation increases propeller speed while reducing boat speed. Cavitation can
seriously erode the surface of the motor lower unit housing or the propeller.
Common causes of cavitation are:
• Weeds or other debris snagged on the propeller
• Warped, nicked, broken, or missing propeller blade
• Raised burrs or sharp edges on the propeller
CLIMATE
Climate changes may affect the performance of the power package.
Over‑temperature faults, reduced available power, and battery shut‑down can
be caused by:
• Higher temperatures
• High humidity
GENERAL INFORMATION
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