Yamaha F6A Manuel D'utilisation page 98

GB
EMU00282
Bow Up
When the boat is on plane, a bow-up atti-
tude result in less drag, greater stability and
efficiency. This is generally when the keel
line of the boat is up about 3 to 5 degrees.
When trimmed out, the boat may have more
tendency to steer to one side or the other.
Compensate for this as you steer. The trim
tab can also be adjusted to help offset this
effect.
Too much trim-out puts the bow of the boat
too high in the water. Performance and
economy are decreased because the hull of
the boat is pushing the water and there is
more air drag. Excessive trim-up can cause
the propeller to ventilate, which reduces per-
formance further. When trimmed-out too
much, a boat may "porpoise" (hop in the
water), which could throw the operator and
passengers overboard.
EMU00283
Bow Down
When the bow of the boat is down, it is eas-
ier to accelerate from a standing start onto
plane.
Too much trim-in causes the boat to "plow"
through the water, decreasing fuel economy
and making in hard to increase speed.
Operating with excessive trim-in at higher
speeds also makes the boat unstable.
Resistance at the bow is greatly increased,
heightening the danger of "bow steering"
and making operation difficult and danger-
ous.
1 Bow up
2 Bow down
3 Optimum angle
3-41