For boaters to realize optimum engine performance under changing weather
conditions, it is essential the engine has the proper propeller to allow it to
operate at, or near, the top end of the recommended maximum RPM range at
wide‑open throttle with a normal boat load. Not only does this allow the engine
to develop full power, but equally important, the engine will be operating in an
RPM range that discourages damaging detonation. This enhances overall
reliability and durability of the engine.
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)
BOTTOM OF BOAT
For maximum speed, a boat bottom should be nearly a flat plane where it
contacts the water and particularly straight and smooth in fore and aft direction.
•
Hook: Exists when bottom is concave in fore and aft direction when
viewed from the side. When boat is planing, hook causes more lift on
bottom near transom and allows bow to drop, thus greatly increasing
wetted surface and reducing boat speed. Hook frequently is caused by
supporting boat too far ahead of transom while hauling on a trailer or
during storage.
•
Rocker: The reverse of hook and much less common. Rocker exists if
bottom is convex in fore and aft direction when viewed from the side, and
boat has strong tendency to porpoise.
•
Surface roughness: Moss, barnacles, etc., on boat or corrosion of
outboard's gear housing increase skin friction and 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.
GENERAL INFORMATION
eng 19
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